Yep, as the others have said most of the big rental agencies have car right there in the parking garage. I rented from Alamo earlier this month. They have me a 2 catagory upgrade when I picked up my car. I had a Chevy Monte Carlo, for 3 days, for $30.32 total including tax! That is WAY cheaper then round trip shuttle/ taxi for 3 people.
When we returned the car I left my friend and all our luggage at the check in/ drop off area, then returned the car, and met up with them. It worked great.