Caught the shuttle to the Rent a Car center which is completely separate and across the freeway from the airport. We got lucky and there was no line at the Alamo desk. Even if there is a line, go to the computer kiosk and skip the line. Our Alamo person was very pleasant and then we went up to the garage and met a couple of Alamo employees to the row of minivans and got to select our own minivan to rent.
Getting back was no problem at all. Just remember that it will take some time to get from the Rent a Car center back to your terminal.
I was very pleased with our Alamo experience.