You'll find compatible people just about everywhere, but the best part of town would probably be Southeast Portland. There are a couple of Deadhead shops on Hawthorne Blvd, like http://www.jamboworldcrafts.com/ (broken link) and The Third Eye, and the
Goodfoot Lounge on Stark is a jamband haven.
You might also want to check out the
Cascade Blues Association - Portland, Oregon.
Also, listen to
KBOO Community Radio online Saturdays at noon for the "Grateful Dead and Friends" show.
I think you're going to like it here!
--
Rob