This year will be my fourth Petit. Went to the inaugural event in '98; have only missed a couple of them since.
Greenville is 100 miles north of Road Atlanta on I-85. I may drive down Friday and Saturday, or I may take a motel near Clemson, about 40 miles from the track (the football team is playing a road game that weekend, no problems getting a room.)
Make sure you're there for the support races on Friday. The World Challenge touring car and GT races are great, plus PLM qualifying. Check the website, they'll post a pdf sometime in August with a schedule of events. My friends have a camper they park in turns 6 - 7 at the far end of the track. I usually park outside the track early in the morning - beats the traffic on the way home - then ride my mountain bike around (which is a workout; Road Atlanta has HUGE hills!!). They also have shuttle buses around the track. You have to be there early to get inside the track, if the plan is to park all the 'Tours together. I mean oh-dark-thirty Saturday AM. Once the in-track parking limit is hit, you're gonna be parking outside. No big deal, but be prepared for that. There are always plenty of car clubs set up inside the track (Beemer, Porsche, Subaru, etc) and you'll see plenty of exotics there (Ferrari, Lambo, Lotus, etc.) Great place for car-watching.
My favorite sign in the campsites:
"PLM - 1000 Miles or 1000 Beers, Whichever Comes First"
To any auto racing fans: this is the best event I've ever been to for meeting the drivers and hanging out in the paddock.
ALMS really means it when they say "For The Fans".
On Friday in the paddock all the teams set up tables and sign autographs, and I mean all the teams and all the drivers. I'm no autograph hound, but it's a real nice vibe. Sports car drivers don't get the pub that NASCRAP or F1 drivers get, they're pretty low-key and friendly. You can kinda sneak into some teams' areas and really look at the cars up-close.
I'm serious, I'll be there. Anyone from our website who's going, be happy to meet you there.
http://www.roadatlanta.com/ 
whippped already! 
) JVT and fst4dr should be coming, and while he might not know it yet Blorton is coming too. There's probably more that I haven't heard about. Glad to hear you're coming down, but a hotel room??