In Lancaster they have a motocross track that looks really cool. Not sure if you've been there but i've included a link to their site. There's a 25.00 entry fee or if you're in a group you can actual reserve it for 4 hours for 600.00.
If my family from Utah comes down in a few weeks i will be renting the track for a 4 hour time period. We can have up to 20 riders on during this time. If you would be interested in riding with us let me know.
http://www.avmotoplex.com/default.htm