ADO is the bus company that runs many routes in the Yucatan Peninsula area. They have a stop at the airport, which has frequent service to Playa del Carmen, about every 15 minutes or so. Personally, I'd take their bus, and from the station to the hotel, it's a 10-min walk or 100-peso taxi ride. Taxi at CUN is quite a hassle, as you need to haggle with the driver directly. I really wish they have something like in GDL, where you buy prepaid taxi passes from a counter inside (price depends on destination), so no one is getting ripped off.