Quoted from here: http://www.fs.fed.us/r5/sanbernardino/ap/questions-and-answers.shtml#placesQ: What about places like ski resorts and campgrounds, where I already pay?A: You won't need an Adventure Pass while parked at places where a site-specific fee is already charged.
The Adventure Pass covers day-use of certain campground, and these will be posted on-site. If you're uncertain whether or not you need a Pass, please call your local Forest Service office or view the listing at Designated Recreation Sites.
DON'T BE ROBBED, if you buy a pass you're paying THREE times to use public forest land
: once with your Federal income taxes, again with a portion of your lift ticket fee collected by the ski area, then a third time to the Forest Service when you buy an Adventure Pass. Print out the page from the Forest Service web site and put it in your window with a note saying you bought a lift ticket and are exempt from buying an Adventure Pass. If you get a ticket, you'll beat it when you show the judge your lift ticket. Just ask the Forest Service people if you TRULY need one if you're buying a lift ticket, then if they BS you show them the page from the web site and see how fast they backpedal.
(Personally I own an Adventure Pass for use in legitimate pass-required areas, but government overcharge really burns me.)