I camped there for a couple of years in my wilder days. The place is a giant, noisy party (at least it was when I camped there) and you will get shite for sleep.
If I remember correctly:
-as long as you have a re-entry pass you can come and go as you please.
- bring as much beer as will fit in your cooler...they don't care.
- No other campgrounds close to the track and hotel rooms are expensive and hard to find...so campling at the track might be your best (only) option.
Enjoy...just don't expect much rest.