Young adults gathered outside the large front windows of the opulent Hotel Parque Central, in the cultural core of Old Havana. Many wore designer jeans. They raised their arms high. For a moment, I thought they were holding lit matches, rock-concert style. Then I moved close to see what glowed in their hands.

Smartphones.

Those teens and 20-somethings, whose entire lives were shaped by the United States’ 54-year embargo, had come to access the hotel’s Wi-Fi. They were using 21st-century technology to connect to a vast world, just as we giddy Americans arrived to devour the lost-in-time mysteries of their long forbidden island.

Of every marvelous, multicolored memory I could share about my September trip to Cuba, this one is my favorite. Even then — three months before President Obama’s dramatic call to “chart a new course” through the re-establishment of diplomatic ties and the easing of sanctions — I sensed profound change.

During an eight-day “people-to-people” educational exchange, my group of 18 saw a nation in flux. That was evident as we walked beneath blocks-long scaffolding abutting architectural restoration projects. We tasted it at numerous privately owned restaurants, called paladares, springing up throughout Havana. We heard it straight from the Cuban people, gracious, welcoming and surprisingly candid about their political and economic frustrations.

The new rules, in part, allow U.S. citizens to travel to Cuba without a special government license, though they will still need to declare one of 12 purposes, including family visits, professional research, humanitarian projects and educational activities. U.S. travelers can bring back up to $400 in souvenirs, including $100 worth of rum and cigars, two no-nos before December.

But as exciting as Obama’s announcement is, “Planet Cuba,” as our captivating Cuban tour guide called it, will remain elusive, and expensive, at least until the country’s infrastructure catches up with pent-up demand.

With the exception of high-end options, hotel rooms are limited. The bed-and-breakfast industry is promising, but young.

Many city streets remain torn up. Few shop owners have the capacity to process credit card charges, though U.S. citizens are now free to use theirs.

Then there’s getting there: U.S. airlines won’t be flying regular commercial routes for a year at the earliest, according to predictions from those in the know.

Airlines seem keenly interested in expanding commercial service to the Caribbean’s largest island, a mere 90 miles from U.S. soil, but they cannot rush in.

Delta Air Lines operates about 250 charter flights to Cuba annually, “and seeds have been planted to allow things to start moving forward” on the commercial end, said spokesman Anthony Black. “But we will have to take aircraft from somewhere else, allocate slots, determine the price of tickets and flight times.”

Sun Country also takes charter flights to Cuba; the airline did not respond to questions about whether it plans to offer regularly scheduled air service there.

For now, most people who want to travel to Cuba will need to go with a tour company, and those prices can be steep.

According to our knowledgeable Cuban tour guide, an estimated 250,000 Americans visited Cuba in 2013, about half of them on sanctioned tours. (The other half likely entered illegally through Canada or Mexico, which could lead to sizable fines and serious heart-racing while clearing U.S. Customs.)

Former U.S. diplomat William Bundy, who has traveled to Cuba for 15 years, predicts that a complete end to travel limits would send 5 million U.S. tourists to Cuba in the next three years, and that would not be good for anybody.

“The tourism infrastructure isn’t there to support an influx like that,” he said. “Tourists would be sleeping in the streets.”

“The last thing you want to do is advertise a product that everybody wants to buy and you can’t provide that product,” he added. “No one will ever come back to your store.”

Frozen in time

Adventurers have long wanted a glimpse of Cuba. The challenge, of course, is figuring out when to experience the island, after travel becomes more affordable but before the country may become overrun.

The U.S. embargo was imposed in 1960, shortly after the American-supported Batista regime was deposed by the Cuban revolution. And there Cuba remains.

It’s that Cuba — of horse-drawn carts galloping down highways, immaculately preserved 1950s car bodies painted turquoise and bubble-gum pink, ubiquitous street music, and not a single McDonald’s anywhere (with the exception of Guantanamo Bay Naval Base) — that drew us there like children to an ice cream truck.

The Cubans don’t want a Starbucks on every corner any more than we do.

“I do think the Cuban people will try to maintain their culture,” said Bob Stacke, retired chairman of the Augsburg College music department, who has absorbed Cuban rhythms during five trips there.

Former diplomat Bundy agreed. He believes that even with an influx of money, Cuba will not turn into just another tourist destination. “I am quite convinced that the Cubans are well aware of this problem and will not open the country willy-nilly,” he said.

Still, say many, don’t wait to find out, and if you can afford it, go now.

“People want to go now because you’re going to see the authentic Cuba,” said Robyn Hawkinson, Cuba product manager for international tour company Go Next. Since its first tour to Cuba in 2013, Bloomington-based Go Next has organized more than 30 trips, and expects to do at least 40 this year.

“I always say, ‘Go now,’ ” said Tom Popper, president of New York-based InsightCuba, the first travel company to receive a people-to-people license in 2000.

“This is such a historical time,” said Popper, whose organization offers six types of tours annually with 170 departure dates. Since Obama’s Dec. 17 announcement, Popper’s Web traffic has increased sixfold, and bookings have tripled.

Tours range in price from a low of $2,800 to as high as $6,000. Many include four- and five-star hotels, entrance fees, most meals and airfare from Miami.

Steve Loucks, spokesman for Twin Cities-based Travel Leaders, predicts that Cuba will eventually be “a lot less expensive than any other place in the Caribbean … and you won’t need to do a people-to-people exchange.”

“But when? I don’t know,” said Loucks, who visited Cuba last February.

“I’ve been telling everybody since I was there, you’ve got to go.

“It was surreal.”

Education in vitamin ‘R’

Surreal, indeed.

My luck in seeing Cuba, especially at this fortuitous juncture, came courtesy of my world-traveling 82-year-old mother, Estelle. Our people-to-people exchange was developed for the University of New Mexico Alumni Association, in partnership with Go Next.

Don’t let “educational exchange” scare you. Yes, we were required to put in eight hours daily of engaging with the country and its citizens in Havana, Cienfuegos, Trinidad and Santa Clara. But “engaging” with Cubans was generously interpreted. At 9 a.m. on our first Sunday, we were welcomed with our first lesson: a tall glass of “Vitamin R,” which stands for rum.

Our days included a concert by the world-class Orquestra de Camara and a demonstration by elite young dancers at an art high school. We practiced our salsa skills at lunchtime (prompted by Vitamin R consumption), shopped at open-air markets and visited master novelist Ernest Hemingway’s retreat, largely intact since he left it in the early 1960s: There’s his typewriter, which he used while standing up, and his liquor bottles, still on a cart in the living room.

We stepped inside Che Guevara’s somber mausoleum, visited a coffee plantation and an organic farm. We toured the massive Christopher Columbus cemetery, where the guide joked that, “until four years ago, this was the only place in Cuba where you could own private property.”

In 500-year-old Trinidad, I hiked with fellow travelers up 167 steps to the top of a bell tower overlooking railroad tracks and sugar cane fields, then climbed down and gave my straw hat to a grateful lace vendor working under an oppressive sun.

One evening before sundown, our group rode in a procession of ridiculously fun and noisy “Coco Taxis,” basically covered seats fashioned onto a scooter, to Havana’s famous Palace Hotel.

On our many scenic bus rides, our 26-year-old Cuban guide, Laura, regaled us with an encyclopedic knowledge of her country, the good and the challenging.

Education is free, through graduate school. Everyone enjoys excellent government-funded medical care. Literacy is reported to be nearly 100 percent. Voter turnout is 97 percent. Forty-five percent of legislators are female.

But with jobs scarce and the average salary $40 a month, people rely on ration packets to make ends meet. (Those packets limit Cubans to 5 pounds of rice per person per month, as well as a pound of chicken and 10 eggs.) The black market is alive and well for everything from fresh fish to car parts to “Breaking Bad” reruns.

Surprisingly, we had lots of time to venture out on our own once our educational day was complete.

One afternoon, I walked past horses, hanging sides of beef and men smoking jumbo cigars and soon realized I was lost. A kind young man with a cycle rickshaw pedaled me back to the hotel.

Toward the end of the week, others in my group and I piled into a taxi, held together with duct tape, it seemed, and took a laugh-inducing, nonsanctioned taxi ride to the beach, where we swam in pristine waters alongside tourists from other countries, for whom Cuba is a regular vacation destination.

I saw the future there: Americans traveling in droves to finally experience a country that is safe, rich in history, abundantly gifted with artists and musicians, fiercely independent and capable because it had to be, and warmly welcoming.

Go now to Cuba. Or go when you can.

But go.