Place a damp paper towel in center of a sheet of aluminum foil. Stack tortillas on paper towel. Cover stack with another damp paper towel; seal foil. Bake at 250° for 10 minutes.
Saute 1/2 cup onion in hot olive oil in a large skillet over medium heat 5 minutes or until tender. Add jalapeno and garlic; saute 1 minute. Add refried beans, salt, and pepper, and cook 4 minutes or until thoroughly heated, stirring frequently.
Spoon about 1/2 cup bean mixture down one side of each tortilla. Top evenly with 1 cup cheese, green onions, and taco sauce. Roll up tortillas; arrange seam side down in a lightly greased 13- x 9- x 2-inch baking dish. Cover and bake at 350° for 30 minutes. Sprinkle with remaining 1/2 cup cheese; bake, uncovered, 5 minutes or until cheese melts. Place 1/2 cup lettuce and 1 burrito on each plate. Top burritos evenly with avocado, tomato, cilantro, and sour cream.