Once you get to the lovely island of Martinique, you have a lot of choices of how to get from point A and point B. What have you used? There's car rentals, of course, and you can hire drivers. Taxis also travel on fixed routes from the airport to the resorts. When you're talking about transportation, you also have to mention the ferries. Called vedettes, the boats connect many of the points throughout the island.
You can also take the ferries off the island of Martinique too...they connect to Dominica, Guadeloupe and St. Lucia. They're cheap too...they average around 6 Euros a ride. Not bad!