May 7th there will be Porsche Club Autocross at Giants Stadium and May 14 there will an M-Club (started by BMW M guys) at the same place.
Porsche club events are the wine and cheese crowd but still fun.
The M-Club attracts many more different types of cars and is more competitive.
Some nice P-Cars should be in attendance on the 7th. There's also a BMW autocross event a bit further south on the same day so that means there won't be too many cars in one place. You should rent a mustang and take it for a few laps!
http://www.motorsportsne.com/2006/results/MSNEAX_040206.htm