If in a public place and they are for you own private use you should be OK
However should you wish to use the images commercially i.e. selling them, then it's a very different matter.
Your entering into the realms of requiring to obtain at least, a Model/Performer Agreement Release if people are in shot and are recognisable and a Property/Location Release for the cars and or venue.
Typical examples of these can be downloaded off the internet, if in doubt get 'em signed up.
Enjoy the show, the problem is normally getting close enough to the cars, not to get folk in the way. Remember to watch for the reflections in the shiney surfaces of paint work and chrome. You don't want loads of photo's of yourself.