When in Playa, I walk down 5th Avenue and buy a Tel-Mex phone card at one of the shops. I believe you have to use one of the Tel-Mex payphones to use it, but I've had no problems in 2 trips calling the US with it. To use it, you follow the instructions....something like...dial 01-800 and then the number you're calling. No problems. There are plenty of phone cards to buy in Playa.