I spent my honeymoon there (4 years ago). Salt Cay Divers was, and probably still is, the only dive operation. My wife and I were the only 2 divers. The dive op was very good - relaxed, friendly, etc. Start by phoning them. We phoned them to book our diving before we had our accomodation lined up (which shows our priorities!), and they booked that for us too - a beachfront place, essentially a motel, whose name I have forgotten. It was clean & in good repair. There was 1 restaurant open (excellent food & service) and 1 place to go for a drink at night.
You go to Salt Cay to DIVE - there's nothing else to do there. For a change of pace, you snorkel or swim. The diving is not challenging - reef & wall dives in clear, warm water. The reefs were in fine condition. Bring all the gear you need - don't plan on picking anything up on the island.