I'm assuming you're referring to the Sea Otter Classic cross country mountain bike race. The past 7 or 8 years or so have used basically the same course with a few changes here or there. About 95% of the course was open to the public (mostly on BLM land).

But for 2006 they have announced that it will be a brand new course, but the map has not yet been made available. Even once the map is released, beware! The maps in the past have been very poor! If you followed the old maps, you would most likely get lost! They showed trails connecting that didn't intersect in real life!

Keep watching at the link that Irulan posted. More information should be posted there "soon".