Alamo was easy! It is right near the baggage claim, and the cars are literally right outside the main entrance, off to the right. Returning your car is easy as well, because you don't have to go too far with your luggage!
We also rented from Dollar in Sanford once. You have to leave the airport main building and walk over to that smaller mall-like building to the left.... Alamo is much more convenient!
There was no line, but that's because it stayed open late for us because Pan Am was 6 hours late arriving... AGAIN! Good Luck!
Holly