I will be going to the NE Motorsports Autocross on Sunday June 8th. It is at Giants Stadium in North Jersey. Been to a few events with this group and Porsche Club, but haven't seen any other G's or Z's at the events. It's a great time. If you are interested but have never autocrossed before don't worry, people are very helpful.
Here are the websites for the two groups:
http://motorsportsne.com/
http://www.nnjr-pca.com/site/index.php
PM me if you want any more info.