If you do a referral and finish your open water certification in Coz, you'll never want to dive anywhere else again! The place is just amazing.
I'm headed down next week with six divers. Two of them are referrals. We've had tremendous success with taking divers down to finish their open water certification in Cozumel. We always go with Roberta's Eco-Dive Cozumel/Scuba Shack. Robert Cwertina has certified several of our divers in the past. He's incredibly patient and not only knows how to dive, he knows how to teach someone else. Those two skills are completely independent.
-Charles