To make salsa: In medium bowl, combine avocado, lime juice, cilantro, garlic, chilies and red onion; toss to thoroughly mix. Add watermelon and toss gently. Set aside.
Over medium heat, heat beans until hot. Mash if preferred.
Place chips on flat, oven-proof plate or cookie sheet and top with beans and cheese. Repeat layers as desired. Heat in oven 10 minutes, or until cheese has melted and chips are hot.
Top with salsa mixture and sour cream.
Notes
Tip: Reserve some salsa to place in bowl for dipping.