Jeannius, Martinique and Gwada are indeed two countries that renting a vehicle is the best option. I had no luck with public transport and though I enjoy the bus adventure, i too will rent a stick shift car.
In gwada a rented from Sixt at the airport. They were expensive and reliable. I also rented from a backyard local. The manual shift car smelled like urine. It was the only rental available between Deshaies and the airport... oh well, lesson learned for 25e per day. Never again!
In Martinique, i waited about 2 hrs for the short bus to la plage... i was told busses dont run at lunch. So I missed out on a second les plages day and wandered until I stumbled upon...i met tourist who shared that it took them all morning to bus from fdf to ste anne. I am not sure if they made it to la plage or the nearby Salines boardwalk.
People's Bar (long walking distance) was my diversion that day. You can pay to use their pool. Ample parking and great music. They close at 6pm daily, if i recall.
As many have pointed out, a rental car is an essential... or prepare to be very flexible as you wait....
