Why not advertise locally? Craigslist would be a good start, maybe postings in some local stores that have bulletin boards. Churches and schools.
Good luck.

We already have (C-list) and had very little response. I figured an audience of like minded folks might be a better option.

How is your community garden coming along? Have you gotten the membership you need? Are there garden clubs in your area? If so let them know about it. Our Community gardens have waiting lists once they are established and people can see them..that's when they want a plot. Is yours ready to plant yet? Ours is not ready yet. We have our space plowed but are waiting for a load of compost this week and then a fence has to be put up. Everything is taking much longer to get done than we anticipated!
Joann

I found people who go to church also like gardening. And perhaps advertise through a health food store? And maybe the Salvation Army.