We are owners at Morritt's Tortuga Club and have been going there for years. Red Sail now runs Tortuga Divers. I dove with them in October and I have to say it was a very pleasant experience. We had not been back since Red Sail took over from the old Toruga Divers owners, but I was pleasantly surprised by the responsiveness of the reservations folks at Red Sail and also the personalized service from the staff at TD and Red Sail when we arrived. The dive boats are clean and well-organized, the dive briefings professional and friendly and the dives themselves were well run, for the most part. Nitrox is available as is any kind of class or instruction you need. I found that the staff is also great about asking for input on dive sites before going out. This is really helpful, especially if you are diving with the same op all week...the staff will work with you to get you to a new site that you haven't seen. The staff is also great at knowing which sites are better for different weather/conditions. Building a good relationship with the staff beginning when you first arrive will really help you throughout the week. I have found them very responsive to diver input and experience level.
I actually took a "scuba refresher" (which they require if you haven't logged a dive inside of a year or two--not sure of the exact time frame) and I found it quite thorough and quite friendly. As I recall, the cost also included a shallow reef dive, so that was ok. I'm all about refreshing skills from time to time

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I also found that the staff will work with you to figure out the best way to plan your week so that you can max out your dive dollar. That's important because diving in Cayman isn't cheap, so the sooner you get by that, the more able you'll be to relax and have a good time. The fact that the staff was willing to help definitely helped me to relax and enjoy the week that much more.
On a related note, Cayman itself is expensive, so my wife and I like to stop at Fosters (grocery store) in town when we get off the plane and stock up on some breakfast/lunch stuff. That way, we're able to spend our money on some really nice dinners and the odd breakfast or lunch (and, of course, diving

). I'd be happy to share some of the other tips/hints that can help you to have a blast in Cayman as well as advice on dive sites, etc. Feel free to PM me if you like and I'll be happy to help in any way I can.
Good luck and good diving!
Mike