I agree, sign up for Quick Silver with
Alamo. I had always used Emerald Aisle, but the Alamo rate was too good to pass up. If you are an Emerald Aisle member and need a QS Corp number to sign up for Quick Silver, just email Alamo and they'll send you a code.
Then with Quick Silver you bypass the line inside the airport and proceed to an Alamo/National kiosk in the parking structure itself.
If you have an existing Alamo reservaton, you'll need to cancel and rebook with the QS number...but check the rate quote for a new ressie prior to cancelling your first one. If it is higher, contact Alamo and let them make the adjustment, as they'll have to over ride the price for you.