I was in Playa Del Carmen last November. I also had never been there before, but I am going back this Nov. I fell in love with it. Very cosmopolitan, yet very authentic. There is a street in the heart of Playa Del Carmen, named "La Quinta" which translates to 5th Ave. The street runs for about 8 to 10 city blocks long. All along the street on both sides, you will find stores, shops, artisans, restaurants, and hotels. It is suppose to be primarily a pedestrian mall, but some vendors do drive their vehicles on it, very slowly of course. You can find some very beautiful artisan crafts, and some very cheap souvenirs. The restaurants vary, from American foods to Argentinian dishes. Some restaurants/hotels are so beautiful you will want to just walk into the lobbys to look around. The beach is only about 1 to 2 blocks from the ave. and most of the beach if not all of it is public (you may want to confirm this on your ship). In playa when you dock from the ferry you can walk to the ave. and just continue walking. Some salespeople will try to sell you a vehicle or a condo, (nice variance in items), however, you can do everything I mentioned on foot.
The people are freindly, and the view is wonderful.
Playa is continuing to grow, however, there is an ecological moratorium on the hotels and condos going up. They do not want it to become another Cancun, which is only about 1 hour north.
If you are going to spend a full day there and are looking for more to do, let me know, because there are some state parks for your exploration and enjoyment, and I am sure your ship will be selling excursions. I have done those too, (xel-ha, and tuluum, and xcaret) if you are interested, let me know, and I will give you my observations and suggestions, otherwise I won't bore you with all of that.
If I don't hear from you, ENJOY!!