How to clean a bike after muddy/sandy cyclocross race (or mountain bike ride)
You should definitely be careful with it, but at many races we employ the use of a pressure washer to do broad stroke cleaning like getting mud, grass, etc off the bike and tires. You need to be careful and use it from a little distance and obviously not get up close on the BB, hubs, etc. but it does a good job of initially cleaning or cleaning between races.

After the race you should do more appropriate maintenance on the bike with degreaser and proper lubes.