You can sign up to race while you're there. However, if you are going to race expert the sign-ups close today, and for beg/sport they close tomorrow afternoon.
I don't see any reason why you couldn't ride. They are not using the gondola to get the racers to the top of the mountain. I would think that it would be open for folks who are there to ride. Lastly, yes, there are a lot of fun trails that you can ride.