I'm interested in private ATV (Quad) rental too. I was disappointed that none of the excursions on my November cruise (Grand Turk, Carnival Cay, Nassua) offer ATV's. I have done the Quad ride at every cruise so far. Jamaica (best one!), Cabo, Calica etc.
Please! Someone post if you have seen any of those guys standing around the pier with Quad rental signs.