Cook sausage and ground beef in a large skillet over medium-high heat, stirring until meat crumbles and is no longer pink. Drain. Stir in jalapeño and next 5 ingredients; cook until thoroughly heated.
Spoon one-third of sauce onto bottom of a lightly greased 13"x9" baking dish; top with 6 tortillas; sprinkle with half of Cheddar cheese. Top with 6 tortillas; repeat layers, ending with tortillas. Sprinkle with Monterey Jack cheese and next 3 ingredients.
Bake at 350° for 30 minutes. Top with avocado, if desired.