tentamus:
I don't know of any volunteer opportunities just yet. this project probably won't qualify as urban agriculture, either. the participants will certainly be urban, but the agriculture will be in Duvall.
check out Seattle's
Year of Urban Agriculture, though. I would be willing to bet you might find some volunteer opportunities there.
your enthusiasm for inner city food security is encouraging, even if we might not be able to put you to work on this particular project.