1. Scoop avocado pulp into a medium bowl, and mash into small chunks. Stir in lime juice, garlic salt, onions, and, if desired, green chiles. Set mixture aside.
2. Cut off crown of pomegranate. Using a small paring knife, score the outer layer of skin into sections.
3. Working with pomegranate fully submerged in a large bowl of water, break apart sections along scored lines. Roll out seeds with your fingers. (The seeds will sink to the bottom, while the white membrane will float to the top.) Remove and discard membrane with a slotted spoon. Pour seed mixture through a fine wire-mesh strainer. Reserve 3 Tbsp. seeds for garnish, if desired. Stir remaining seeds into avocado mixture. Sprinkle evenly with reserved seeds to garnish, if desired. Serve with tortilla chips.