Jeff:
October can be real nice, or real cold and rainy. Of course, sailing in the "off" season brings other opportunities... When you say "Seattle" do you mean you want to leave from Seattle itself, or are you willing to travel an hour or two north by car to get to the San Juans?
Also, there are a few large classic sailing vessels around that might be able to accommodate you.
Something like this?
Alcyone Sail Training
Schooner Martha Foundation
David