I can only comment on my local laws (Pennsylvania), but I imagine they are similar.
Anyone caught watching a street race is charged with "participating in racing on a public highway" (yes, if you watch you are considered to be participating by encouraging the crime). Same penalty as the guy with the car in motion.
I forget the penalties, but they include: stiff fine (at least $500 IIRC), 1 year suspension of license, and MAJOR insurance premium jump, if they don't dump you. If the insurance dumps you, you are put in the "high risk" pool and pay even more out the nose.
My advice: Spend a sawbuck and go to a legal, safe, controlled, sanctioned drag strip, race to your heart's content, and never once worry about getting busted for anything.
