The good thing about Alamo is that you do get to pick your own vehicle from the inventory in stock at the time. If you're not happy with the available selection in your category once you get to the garage, it's worth going to the booth (in the garage, not back in the airport) and talking to someone. Have a look around first and see if there's anything else you like the look of and don't be afraid to haggle hard. They want to do the deal.
ETA: Oops! After posting I've spotted that you're not picking up from the airport, so you'll probably be choosing from an inventory of one. Sorry.