I just got back from Playa del Carmen Sunday night. It was beautiful weather there, you are going to love it!
I didn't do any Cozumel dive as I was staying in Playacar and I thought that Cozumel had stronger current drift dives but I did one at a site called Tortugas that had a fast current and it was awesome. Felt like I was flying and we saw a bunch of turtles. Now I can't wait to go to Cozumel and dive the sites over there!
The best dive, hands down though, was the Cenote dive. Wow. I'm still blown away by how beautiful it was. We did Dos Ojos which I highly recommend. Lots of formations, 'cave like' areas where you're in darkness and areas you go through where the light shines in. So beautiful. Go in the morning before it gets too packed with afternoon divers. We only saw divers in other sections, never ended up crowded or grouped up. I'm AOW with about 30 dives, my buddy was certified many years ago and hadn't dived in almost 20 years. We did our Playa del Carmen dives first (4 day, 1 night) to get ourselves settled and comfortable and did the cenote last. If you have good trim and buoyancy control you'll be fine in the Cenote. There we no 'closed in' areas at Dos Ojos, it was very open (for being in an underwater cavern). I'm hooked and cannot wait to go back and do another one!
Have a great trip!
ETA to agree with TS&M (who I have learned everyone should pretty much do as she says) about going with a reputable guide, etc. We were lucky that it was just me, buddy and guide, as well as it wasn't very busy.... even through we saw a lot of divers above ground, we only saw lights below and only passed a couple divers going the other direction once.