Friends of ours kept their 38' catamaran on a mooring in Georgetown for 2 of the past 3 years, bringing it to the States the end of last year.
There are haulout marinas in St. Martin that bury the keel in the earth for hurricane season. On the Sandy Ground Road to the Lowlands (Basse Terre). We have a friend there who also takes care of yachts for people, but I'd have to check to be sure he's still doing it - if you want, I'll ask him.
One of the best resources for cruising boats in the Caribbean is BUDGET MARINE
It's a big operation now, but I think they're still a friendly lot who can answer your questions and offer up to date information. But be sure to give them a idea of what you expect to spend - nothing's cheap on St. Martin.
There's a lot more crime in the Caribbean now, quite different from when we were living and cruising there. There's a marina in St. Martin where boats have been left in Anse Marcel, but I don't know if it's still running. Also Oyster Pond, but I don't recommend it there. And Simpson Bay Lagoon.
I'll try to find out a few more places, though I hope somebody else will chime in with some current info.