Anyone planning to nibble their way across the Minnesota State Fair will find considerable financial payback from the $4 investment that is this year's edition of the fair's "Blue Ribbon Bargain Book." It's all about money-saving coupons from 88 food-and-drink fair vendors, including $2.50 off guacamole and chips at Tejas Express (the Garden), and buy-one-get-one-free offers at Green Mill (Baldwin Park) as well as all five Root Beer Barrel outlets. It's sold at the State FairWear gift shops (Visitors Plaza, Lower Grandstand and Warner Coliseum) and at Bargain Book & State Fair Poster Carts throughout the fairgrounds.