I have rented a car several times. Because of the mountainous terrain ( zig zaging roads) driving is tedious and takes time. But sometimes it is the best option. There will be mirrors on the U pin turns in the mountains ti see on coming cars ( and dump trucks). If you can acquire a boat taxi to some of the places, that might be the best option ( less stress and quicker).
I have drove from the airport several times to Gros Islet. The middle of the drive is through the rain forest which can be a good drive or a bad drive, depending on the conditions.
And unless things has changed you will have to purchase a temporary driver license also.
SXM??? Wendell