Don't know when you plan on starting, but Skalkaho can experience closures due to slides/washouts caused by melting snow in June. We intended to ride it in early July of 2011, but it was impassable at the falls. Earlier in the trip we fortuitously ran into an ACA employee at a hot spings. He is the one who told us about Rock Creek Rd. as an alternative out of Philipsburg.
When I rode it this year, part of it was officially closed south of the falls due a slide, but I was able to get through with a bike. Only had to walk a short distance, and the space between the barriers was wide enough to squeeze through with the loaded bike. There was heavy equipment up there but no road crews on a Friday afternoon. If you call 511 you reach MDOT's automated road conditions report. The best source of real life conditions are the locals. This year, the slide had already happened when I started my trip from Missoula. I cheked with the shop on U.S. 93 in the center of Hamilton and Red Barn on day one and was told I should be able to get through. Since I was riding it from north to south later in the trip, I inquired at the Gem Mountain retail store in Philipsburg and then again at the mine itself. Everyone thought I would be able to get through.
Closure can be a good thing. The only vehicles I enountered between Gem Mountain and the small, U.S.F.S. Black Bear Campground outside of Hamilton were a convoy of dump trucks taking dirt up to a small section of the road north of the pass that was being graded.