The beach in Playa del Carmen is an eclectic blend of people from all parts of the world. I have noticed that on one end of 5th Avenue there definitely seems to be sort of an Italian district. So in keeping with that it seems that the beach at that end follows suit. Therefore don't be surprised to see topless sunbathing on some parts of the beach, for as I understand it, it is a common happening on European beaches. I didn't know it happened until I was down at the beach one day and happened to choose this particular area to relax in for the day. It certainly wasn't offensive in any way and no one made a big deal about it. Thinking back on this I can't remember noticing this on other parts of the beach.
PS: Want to come play in Playa del Carmen?