Hello! This will be my first time hiring a car, so I need all the help I can get.

WHERE/WHEN: So, I'm going for a Deep South road trip with the girlfriend. Two weeks, starting and finishing in Atlanta. We land on Sunday May 3rd at about 3PM, leaving around the same time on May 16.

THE CAR: Somehow I have my mind set on a convertible. The sites all seem to say 'Ford Mustang or similar'. The best deal I can find is going for Alamo, via Netflights.com.

They're quoting me £392 (about $595) for 13 days. Includes: Unlimited Mileage, Collision Damage Waiver, Loss Damage Waiver, Theft Protection Insurance, Local & State Taxes, Supplemental Liability Ins., Airport Surcharge, Zero Excess

Is this good? Can anyone find a better deal? Is Alamo good? And how does it all work? I've heard people pay, and then go pick a car from a big parking lot. Does it really work like that?

I've also heard that you're never guaranteed what you get, and people get upgraded. Do I go for an 'Intermediate' and hope to upgrade to a convertible?

Also, do I want a Mustang? I'd be interested to know if anyone has experience renting from Alamo ATL and can say what cars they have.

Also, also, If I land at 3 in ATL, what time should I book the car for?