Cayman's a great place! I was planning a vacation there myself in August. (Got sidetracked to abother destination...) But Neptune's Divers came VERY highly recommended to me from several different people. Their prices are comparable, and they will not take out more than 8 divers.
As far as Stingray City...if you do this as a dive, there's not too much to worry about. Most of the cruisers do the snorkel trip out there, which is in waist deep water. We had a great guy take us out there for the snorkel trip. He told us if we didn't mind, we'd go snorkel somewhere else and go back when the cruise ship ppl. left. (Wasn't a diver when I went last time...WAAAAHHHH!)
Anyway- have TONS of fun. It's is every bit as beautiful as the pictures you see, and the people are very friendly there.
Kristey
PS..if you feel like an expensive dinner out one night...DO NOT miss the Wharf! YUMMMMMMMY!