Saute the beef and garlic in oil in a small skillet until browned, 5 minutes, breaking up with spoon. Stir in chili powder, cumin and salt; cook for 1 to 2 minutes.
Mix tomatoes, green pepper, red onion, jalapeno and salt in small bowl. Set aside.
Peel, pit, mash avocados. Place in small bowl. Stir in lemon juice.
Preheat oven to 400 degrees F.
Cut the tortillas into quarters. Place in single layer on ungreased baking sheets. Spoon 1 tablespoon refried beans on each piece, then top with 2 teaspoons beef filling and 2 to 3 teaspoons shredded Cheddar cheese.
Bake in 400 degree F oven 7 to 8 minutes or until cheese is melted and edges are slightly crisp. Place on serving platter. Top with avocado and salsa. Serve immediately.