Not that I know of, the car rental place will shuttle you to the port, though. The last time I rented a car, I dropped my hubby and luggage off, returned the car and they shuttled me back. By then the porters had taken the luggage and my hubby had moved up in the line.
If you are flying in the same day as cruise and just renting the car to get to the port, you are better off and cheaper to just take a taxi. It is very close and I think the last I heard it cost $15. Its a pain to get thru the guard gates in a private car, much faster with a shuttle or taxi/bus.
It's only 2 miles from FLL to the pier. You can literally see the ships from the runway. A cab would be your best bet unless you're coming in early and want to sight see. If so, drop the rental at the airport and grab a cab. It can take longer to get out of airport parking than to get to the pier.