Once on the island, transportation is not difficult to arrange. Taxis meet incoming flights at the airport and incoming ferries downtown. Car rental agencies are at the airport and in town. They also provide free pickup service at your hotel or guesthouse or at the Steamship Authority. The latter two are at the airport.
Mopeds are faster, but inexperienced drivers can get in trouble with sand on the roads.
Rental agencies can inform you of the regulations. Do not ride bikes on sidewalks or mopeds on bike paths, and heed one-way street signs and other street signs. Front and rear reflectors are required. All are within walking distance of the ferry dock. Ask someone about their trip to the island, and the first thing they'll tell you is how much they loved where they stayed.