I've been up there spring, summer and early fall--and not for a couple of years, so take this with a grain of salt. There has always seemed to be an official policy (No accessing backcountry via the ski area) and an actual enforced policy (don't be a jerk and you can pretty much do as you please). That means if you're skinning uphill, stay well out of the way of downhill skiers, preferably off the groomers...which you probably want to do for your own reasons anyway. If bootpacking, don't do it where you'll trash groomed surfaces going uphill or down. And if you pay for a lift ticket, be somewhat surreptitious about cutting across towards Illumination Rock/ZigZag Glacier from the top of the Palmer Lift.
Since you're unfamiliar with the area, be aware that fall line descents will take you far from the ski area into areas of wandering canyons, steep trees, meadows, etc. Bear sharply toward skiers' left if you ever intend to see your car again.
Hope that's helpful.
Mark
