RE: Mexican food in Playa del Carmen
I've never been to Playa del Carmen but I've been to Cozumel many times and must say I've never seen pineapple on a taco. Usually a corn tortilla with pork,onion, and cilantro.
If you like seafood you will be in luck. I don't know about Playa, but in Cozumel most restaurants post a menu outside so you can stroll around and see what they have to offer.