You may not know what to plant yet, but now is time to prep your worksite. After reaching consensus, you know where the garden will be. Post on social media to recruit volunteers, organize to meet for a day, and prepare the site to garden.
Worksite prep involves several decisions and tasks like clearing debris, till or no till, setting up irrigation, putting up a fence, and more. If the community decides upon raised beds, use this day to construct them. If you don't like tilling and prefer to smother, prep a few months before the growing season. Your gardening plans can be as big or small as you like, and resources such as time allow.