Most of the cavern tour cenotes are south of Playa del Carmen. It's about an hour's drive from Cancun to PDC. I know that there are some Cancun dive operators who will run cenote tours from there, but it will make a long day, and I would guess they would be more expensive, just due to transportation costs. Especially if you are planning on two or three days of tours, I think you'd be happier in PDC or even further south, in Puerto Aventuras, Akumal or Tulum. This will also give you a wider choice of tour guides.
There are a lot of good guides. I have a couple I particularly like -- my good friend and dive buddy Jason Renoux (jason@essentialdivetraining.com) and Natalie Gibb and Dennis Weeks of Diablo Divers (nat@diablodivers.com). They're really nice people and also good company, and know the caves well. But there are a lot of other choices as well, and some of it may depend on where you decide to stay.
My personal favorites for caverns are Grand and Dos Ojos, but Taj really does have some lovely halocline effects if you are there at the right time of day. I did not think that much of the cavern at Chac Mool, but I know other people who have loved it.