I would seriously suggest to rent a car. It not nothing to be afraid of or need hours of orientation to get used to. There is literally one main road that loops the island with turn off to the various beaches. In May you should be able to get a car for $20 a day. One way taxi from GC to Orient is $15 for 2 people. SXM is the first foreign country I drove in and was nervous my first time, but after pulling out of the rental car lot I realized it was no big deal.

http://taxistmaarten.com/zones-rates/