New to Seattle area
Just moved to Bellevue. Been riding St. Eds and Duthie, but looking to hit up Galbraith, maybe this weekend if the weather's good.
I have an AM rig ('06 Giant Reign) and a DH rig ('11 Mongoose Boot'R).
Also have a truck if shuttling's an option.
No shuttling at Galbraith. People do sometimes push their DH bikes up to the top. You could always bring both and see which one you like better.
Just in case you haven't run into 'em yet, here are some web sites.
Evergreen Mountain Bike Alliance - Washington's Largest Mountain Bike Club
I would suggest you bring the trailbike on Galby. Nothing up there warrants a big bike.
The folks that usually push a big bike up do that because that's often their only bike - especially high school/college students.
Shuttling is tricky and best off the interwebz as places that get popular often end up getting shut down. If you start to connect with local riders, those places will present them to you.