1. Wipe chiles clean with a damp cloth and remove stems and seeds. Chop in a blender until finely ground. Add tequila, lemon juice, 1/4 cup water, garlic, oil, oregano, and 3/4 tsp. salt; blend until smooth.
2. Cut pork across grain into slices 1/2 in. thick and 3 to 4 in. long. In a bowl, add meat to marinade. Chill at least 15 minutes and up to 24 hours.
3. Lift meat from marinade and thread strips onto skewers. Lay skewers parallel and about 2 in. apart on a baking sheet. Pat marinade onto meat.
4. Prepare a charcoal or gas grill for direct medium-high heat. Lay skewered meat on oiled cooking grate (close lid on gas grill). Cook, turning often, until meat is well browned and crusty, about 20 minutes.
5. Meanwhile, in a 1 1/2- to 2-qt. pan over high heat, bring 3/4 cup water, the rice, tomato sauce, and remaining 1/4 tsp. salt to a boil. Reduce heat and simmer, covered, until liquid is absorbed, 15 to 20 minutes.
6. About 5 minutes before meat is done, put beans and their liquid in a 1-qt. pan and cook over medium-high heat until bubbling, about 5 minutes.
7. Lift cooked meat to a platter and cover with foil. Heat 1 or 2 tortillas at a time on grill until lightly browned but still soft, turning once, 30 to 40 seconds. Stack on platter beneath foil to keep warm.
8. Preheat oven to 200°. Warm serving plates in oven. Remove meat from skewers to a board and cut into 1/4-in.-wide strips. Lay tortillas flat. Toward one side of each, fill with guacamole, crema, pork, beans (including most of liquid), rice, cheese, and cilantro; divide 1 cup salsa among burritos. Fold over sides and roll up tightly to enclose. Work quickly during assembly to keep burritos hot, and serve on warm plates; if burritos cool off, you can wrap each one in lightly oiled foil and heat in a 350° oven for 10 to 20 minutes. Serve remaining salsa in a bowl to add to taste.
Quick Tip: Buy ancho chiles, crema, and cotija cheese at a Mexican market or other specialty-foods store.
Note: Nutritional analysis is per large burrito.