You have to take the shuttle (10-15 mins ) from the Terminals to reach the main Rental Car center where all the car rental are at. The problem is this is when the shuttle reach the terminals , you have a giant wait for everyone getting online to get the car.
Make sure you get on the budget fast break program as that line is a little shorter. I waited 30 mins even with Fast break..
Returning the car is another 30 mins (15 to return ) & another 15 on the bus... give your self at least 45 mins more if you rent a car to make your check in & flight.