"Enter at your own risk" is synonymous with enter at OUR legal, financial et al risk. "Our" being the entity that will have to dole out the $$ when something does go wrong.
There is no such thing as a solid disclaimer, anymore, when it comes to public lands, roads, etc.
As far as the boulders go, I seem to notice them on the road every year when pictures are taken. Granted, they may not all be the size of a VW bug, however, it only takes a fraction of that weight to take someone out.
