Combine first 5 ingredients in a small saucepan. Bring to a boil; reduce heat, and simmer, uncovered, 25 minutes, stirring frequently.
Cut each tortilla into 6 wedges. Place wedges on an ungreased baking sheet. Bake at 350° for 5 minutes on each side or until crisp and golden. Set aside.
Place lettuce evenly on 2 salad plates. Spoon meat mixture evenly over lettuce. Sprinkle 1/4 cup tomato, 2 tablespoons avocado, and 1 tablespoon green onions around the edge of each salad. Sprinkle cheese evenly over meat mixture. Top each salad with 1 tablespoon sour cream. Serve with tortilla wedges.