I5 to I 405 and unless you can go at 2 to 3 am, then it is going to be traffic. Seattle is the worst, and not getting any better.
There just isn't another way around unless you want to really go out of your way. You could take the scenic route, and get on Hwy 18 at Federal Wayish, and then right after you pass I90, continue straight on and youll be on 202, then watch for 203 and stay on 203 to Hwy 2. Turn west on 2 for just a bit and the head west again on 522. It will take an extra hour at least but its a pretty drive.