In a blender or food processor combine the avocado, lime juice, cilantro, mayo (or greek yogurt), and salt and garlic powder for the sauce and pulse til smooth. Add 1 tablespoon or milk or water at a time until desired consistency is reached. (You just want it to be easily spreadable and smooth) Set aside.Toss slaw or cabbage with 1/4 cup mayo and juice from 1/2 of a lime. Set aside.Grease a skillet and preheat over medium heat. Add fish pieces. Drizzle juice from 1 lime over fish, then sprinkle with taco seasoning and saute over medium heat 6-8 minutes until outside is browned and fish is tender.Assemble tacos by dividing slaw, fish, and avocado sauce between tortillas. Serve with additional cilantro and lime wedges.