Yes. Some companies allow you to take their cars to STJ and some do not. I always rent from Dependable. They are just outside the airport and will come and get you when your plane gets in. Car rental companies at the airport add a 10 or 12% tax to the cost because you are picking up at the airport. Taking a car to STJ is roughly $50 round trip. One passenger is $12 round trip, so if there are a couple of people going, it's quite a bargain because you won't have to take a taxi everywhere in STJ. Go to Cinnamon or Hawk's Nest for great beaches and grab lunch at Skinny Legs in Coral Bay. Just get in line early for the trip there and back so you don't miss the ferry!