Finally you have a site...and better yet you have permission to use it! You have access to water and you are ready to search out like minded people and get this garden growing! First step is finding other gardeners so that you can make plans for your garden. Trust me this is much easier now that you have a location. People know that you are serious about making this happen and that you will follow through.
One of the easiest ways to meet a large number of people is to host a free class! This will be easiest in Spring when everyone who wants to garden is still making plans. Many libraries will allow you to borrow a room for your class as long as it is free. Remember those Master Gardeners I told you to make contact with? This is where they come in. They should be willing to provide a presenter for your class free of charge. The Cooperative Extension Office is also an excellent place to find a presenter. You want your class to be about gardening, if possible make it about community gardening!
It will be up to you to advertise your class. Put up posters and enlist anyone who has expressed interest up to this point to put up fliers as well. Get on Facebook and Craigslist and list your class as a free community event. Call up your local paper and get a short blurb in their events section. Stop by the nursery and leave a flier there...you really need to get the word out because you need a big turn out for your free class. Contact your cities Parks and Rec department and make sure they have your contact information and information about your free class. Parks and Rec may also make a Facebook notice and put you on the cities listing of local events.