Preheat grill pan over high heat. Coat chicken with olive oil spray; season with Mexican seasoning and salt. Grill 4–5 minutes per side; cut into bite-size cubes. In bowl, mash avocado with fork; stir in pomegranate seeds, juice from 1 lime, and minced garlic. On each of 4 plates, divide chicken and guacamole among 2 (6-inch) corn tortillas; top with 2 tablespoons sliced red onion, 1/4 cup shredded red cabbage, and 2 tablespoons crumbled low-fat queso fresco.