I'd second RainyGrlJenny - my husband has been to a couple of the meetups through there (there are other meetups, a new one in North Seattle I think, some people living in the South end do some stuff too), and we went to one potluck at the CSPC. Not sure if you're an introvert or extrovert - I did not like the potluck, I'm pretty shy, I think the meetups would be fine even for me solo though. He came out of them with an invite to a board game group and met some nice people with similar interests. I do believe that networking and making friends is most useful for finding people to talk to/ask advice from as well as date, and it seems kinda vital here in the Seattle area.
I'm always open to answering questions or whatnot about poly too - feel free to PM me if you have any random shit to ask about anything