To prepare tomato salsa, combine first 8 ingredients in a small bowl; cover and chill at least 1 hour.
To prepare mango salsa, combine mango and next 7 ingredients (through 1/8 teaspoon salt) in a small bowl. Cover and chill at least 1 hour.
To prepare fish, combine 2 tablespoons lime juice, 2 teaspoons olive oil, cumin, and garlic in a large zip-top plastic bag. Add fish to bag; seal. Marinate 15 minutes, turning once. Remove fish from bag; discard marinade. Sprinkle both sides of fish evenly with 1/4 teaspoon salt. Place fish on grill rack coated with cooking spray; grill 4 minutes on each side or until fish flakes easily when tested with a fork or desired degree of doneness. Flake fish into large chunks.
To prepare tacos, place tortillas on grill rack coated with cooking spray; grill 10 seconds on each side. Divide fish and cabbage evenly over one half of each tortilla; top each tortilla with salsa and 1 tablespoon sour cream. Fold tortillas in half. Serve with lime wedges, if desired.