Aside from having to drive to most mountain biking, you're really centrally located to get out to I-90 trails, capitol forest trails, and even Port Angeles trails. Now if you're talking dirt jumps, I'm not really in the loop there anymore. Someone else could probably chime in.
The University Place skatepark is fun, and so is the Gig Harbor skatepark. Parkland is sweet, but last time I went we had to sneak in because of security guards.
Give Tacoma a chance- I lived in that area for a few years and grew to like it a lot. Don't listen to the haters!
Downtown is built on a big hill and is full of stairs and it it fun to have a few ales and sandwiches at the local brewpubs and shuttle back up on the bus. Havent done it in a while, but is highly enjoyable. There are sweet dirt jumps in S.side. I have a big BMX and have been riding S.side for years, and still love it with all my heart. Dont expect to see alot of MTBrs out here. Every day I find new stuff.