We just did a week (Thanksgiving) in Playa del Carmen at the Occidental Grand Xcaret for a mere $850 (airfare not included) for my wife and me. I dove for three days in a package ($235.00 I think) with Playa Scuba and got to dive Cozumel one day, a Cenote (Dos Ojos) the next and finally a shark dive and reef dive in Playa del Carmen on the third day. Was worth it! The Occidental Grand is an all-inclusive about an hour south of Cancun. And of course, any trip to Cozumel is full of great dives...I recommend Aldora divers there; they only take small groups and also offer hi-cap tanks for those of us who are air hogs, as well as Nitrox.