The site is directly off of I75. There are hotels all over off of the highway, but you'll probably want to go a bit South of the site to get one. I don't remember how many there are North of the site between GA and TN. I mean, I know there are a couple, but I don't remember if they are skanky...
Yeah, as far as Atlanta airport vs. Chattanooga airport it's a toss-up. If you're coming in around rush hour times the Chattanooga might be a better bet if the prices are similar. I'd totally pick whichever one was cheaper. I can get from my house (20 mins South of our event site) to Chattanooga...