Drift Diving isn't a difficult thing to learn and your Dive Master will brief you a little bit on what you need to know on the way out to the dive site. There's also a drift diving specialty course you may want to consider investing in to get the maximum enjoyment out of your Cozumel diving.
The big thing to remember about drift diving is don't fight the current or swim against it. Instead, relax, relax, and relax. Maintain your neutral buoyancy in top condition and "fly with the drift".
As to finding the best op, the first thing I would investigate is safety issues. This is always my primary concern. Ask if the operation has a radio on board, oxygen, first aid kit. Affiliation with the Hyperbaric Chamber is a good sign, too. Organization and equipment upkeep is something else to take a close look at. Check how they have their gear stored, for example. Is it properly rinsed, neatly hung, in good condition? Ask to try on the equipment you'd be using and look at it closely for fit and function. Another really important thing to ask about is whether the op is planning to take out a boat with divers of mixed experience. The temptation is great to want to do this because it's easier to fill the boat that way. But if you find out that the op has in mind sending you out with a mixed experienced group-for example, beginners mixed with guys who have logged more than 50 dive --then ask nicely if they'll send an extra DM along - one to take care of those who are more experienced and another to watch out for newer divers. This is the safe thing to do.