Good advice from Ed. The Reef Playacar is the first AI in a long line of AI's headed south in Playacar. We've stayed next to it at Riu Palace Riviera Maya a bunch of times now. I've not stayed at the Reef but have looked at it from our patio the couple times we've gotten rooms on that side. The Riu Palace is something else. VERY extravagant. Might be the nicest place on that strip of AI's (for certain of the other Riu's) but I've only seen the other places from walking the beach in front of them.
I've seen the dive boats from Reef (and Riu who's on site shop is Scuba Caribe) both leaving full and out on the reefs, also full. A mix of experience levels but most look beginner. In fact on more than one occasion we've been heading to a dive site, seen an AI boat coming and hustled to get our gear on and in the water ahead of them to stay out of the meat grinder of fins, arms and legs.
If you look around there are a number of shops in Playa with great reputations on the board. Ed has mentioned a couple, I always dive with Jason (playacountryboy on the board here) of Fantaseadive - was there with him again a couple weeks ago. pretty much any place in town is a $5 cab ride from the Reef Playacar.
Most any shop can set up ocean, Coz and cenote dives. If you've never done a cenote I HIGHLY recommend it. Totally different experience and I'm getting to the point where I like them better than the Playa ocean dives...well, maybe not!!
When we were there a couple weeks ago vis wasn't what I'm used to because of recent storms but the dives were still nice. The reefs are in decent shape, plenty of schooling fish, eels, squid, an occasional pipefish or seahorse, barracuda, rays, etc. Every once and a while something bigger will pop in for a visit.
If you search for posts by playacountryboy Jason has a ton of videos he's done over the years of taking people out - should give you a good idea of what to expect!