Can I sue the race track or a person who hit me during a demo-cross car race if they broke the rules?

Without knowing exactly what kind of release you may have signed prior to entering into this event, I would say, generally, that you probably can't sue. It would seem to me that this type of activity will fall under the doctrine of "Assumption of the Risk."  That is, since the chance of a collision is an inherent part of car racing, you have probably assumed any risk involved with being in a collision.   This holding is from Knight v. Jewett (1992) 3 Cal 4th, 296.  The Court, in addressing something similar to your question, said that even when a co-participant violates a rule of the game and may be subject to internal sanctions prescribed by the sport itself, no legal liability will attach.  The Court reasoned that to impose legal liability would, in effect, discourage vigorous participation in such sporting events. The Court tempered this finding by stating that a co-participant does have a limited duty of care to refrain from intentionally injuring another participant or from engaging in conduct that is so reckless as to be totally outside the range of the ordinary activity involved in the sport. I hope that helps.