I think it's a good idea in theory-sharing a piece of your property so that someone else can garden on it. But, I'm not sure I would be up for it especially if I was the property owner. First of all, you don't really know who's showing up and since you haven't hired them they can basically do whatever they want on your property when you're not looking. And what about liability? What if someone steps on your rake and takes an eye out?
Then there are all the logistical problems. Who's going to take care of the daily or weekly maintenance? Who's paying for the supplies? What if you don't like what the people are growing or what if they take off halfway through the project and you're left with most of your lawn removed and a giant pile of sod in your driveway? I think I might know-call a professional.
I'm not saying no, just think before you share or plant. Start out small with a tiny plot that isn't going to impact the rest of your yard or drive your neighbors crazy. If you have a good experience, go from there. Trust your instincts when you meet with people and ask them what their gardening experience is. If they seem really young and naive direct them toward a community plot and look for someone how actually knows how to garden and who seems responsible enough to commit to a plan.