We recently rented a car at the port, a local saw us in line, asked us if we were renting a car, took us to the back of the building, and pretty soon drove us to the rental car place. Definitely off-site, and told us to return the car at 4 p.m, not to the port, but to the rental place. That worked perfectly, we got there at 3:55 p.m, they drove us back to the port area, we had time for a couple of cocktails outside while we were getting our group back together again to see everyone's purchases (a lot of 1st timers to SXM), and then headed back to the ship.

I want to say the company was called Sunny rentals. Worked great for us. About $80.