@
ichitaka05 are you thinking east coast/west coast/mid America yet, or open to all at this point?
- September - October
- Georgia
- Atlanta Motor Speedway, Road Atlanta, or Atlanta Motorsports Park or all of them.
Fall is always better for a car gathering just about anywhere.
Georgia because nearly all interstate and air traffic leads (or can lead) there.
I know AMS hosts autox in their parking lot all the time, not sure about Road Atlanta. Also, at AMS you might be able to get some type of discount on one of the driving schools and driving "events" held there on the speedway itself.
I'd personally favor AMP just because its a road course and its more designed specifically for events.