We flew in a day early. Rented a car at the airport, and drove to the Radisson at the Port. The next morning, we dropped the car off at their office just a short distance from the Radisson. From there, we hopped on the shuttle that they run to the port. He dropped us off at the Radisson on his way to the port. From there, we got on the hotel shuttle that took us to the port.
After the cruise, we got on the car rental shuttle and went back to their office to pick up another vehicle, stayed at the Radisson another night, then drove to the airport and dropped off the vehicle.
You really have to be careful with the gas. They want you to fill up the tank or pay an arm and a leg if they do it. Only trouble is, there aren't any gas stations between the port and the airport. Fill it up at the port.