Combine first 5 ingredients in a bowl. Stir well; set aside.
Place pinto beans in a bowl. Partially mash with a fork, and set aside. Heat oil in a medium nonstick skillet over medium-high heat. Add onion and garlic; sauté 3 minutes or until tender. Add coriander, flour, cumin, salt, and pepper; cook 1 minute, stirring constantly. Add onion mixture to beans, and stir well. Cut 6 (4-inch) squares of wax paper. Divide bean mixture into 6 equal portions, shaping into 3 1/2-inch patties on a wax paper square.
Invert patties onto a baking sheet coated with cooking spray; remove wax paper squares. Broil patties 4 minutes. Carefully turn patties over, and sprinkle with cheese. Broil an additional minute or until cheese melts. Place patties on bottom halves of buns; top each with 1/4 cup salsa and top half of bun.