If you grade on a cost-benefit curve, La Vallesana might be the best restaurant in St. Louis. For less than $5 you can have three tacos al pastor: smoky pork, grilled pineapple, onion and cilantro on corn tortillas. Give each a squeeze of fresh lime and a slather of fiery red or green salsa, and you have the perfect meal. Can't live by tacos al pastor alone? (What's wrong with you?) Try a taco made with meltingly tender barbacoa or earthy beef tongue. Burritos are very good, especially with spicy chorizo. For a messy, overfilled delight, torta sandwiches deliver the goods and then some.