I think it is possible to get married in Playa del Carmen's Catholic church. I can try and find out more about it, just give me a couple of days. However, the religious ceremony does not make the marriage legal; you have to do a civil ceremony with a judge. I also doubt that the Catholic priest would do the ceremony in English, but that's just a guess.
Most foreigners that get married here prefer to have a beach wedding on the Caribbean paradise beaches of Playa del Carmen, so this question doesn't come up that often. I'll check!