I personally wouldn't want to live in the Seattle metro area, it's just a little to big for my taste, but they definitely have some pretty good stuff to ride, and adding more to the inventory.
I'd suggest...
Bellingham - Good stuff in Galby and close to B.C.
Wenatchee - Not a lot of FR/DH but some very nice trails.
Spokane - Nice FR/DH trail system at Beacon Hill and close to Rossland BC, but the economy in Spokane itself is a little depressed.
Port Angeles - I really like the town and surrounding area, the riding at Dry Hill doesn't get much better than this, but Port Angeles is kinda isolated.
Olympia - Capitol Forest rocks, but not a really FR/DH area. I believe they are working on building new FR/DH trails.