Welcome Dex,
I too am thinking about doing the STP, and have partaken in a few of the Cascade Bike Clubs training rides. I'm still not sure about the group riding thing. I get scared when people act in a reckless manner ( at least to my perception). But I'll keep going to the training rides and see what happens. I'll keep you posted. I won't be there every weekend, but if you do show up I'm in the 12-14mph group, the blue SOMA bike with orange handlebars.
Once I get this training schedule figured out a bit I'd love a social ride to Redhook