Very excited to hear about your new community plot. That is great that you were allocated space and I can't wait to hear how the plots are set up. Generally every community garden has a set of "garden etiquette" rules depending on who is setting the garden up.
My garden is part of the Portland Garden and Recreational Program so it may have more formal rules than your plot will have. It seems like the biggest no, no is to have a weedy plot. We have rules on weeding like we must show that we have made a start on weeding our plot by May 1st of each year and by June 1st half of our plot must be weeded. Ask if there are any garden amenities included. For example we have a water hook up for each plot. The water is turned on from March 30th to October 30th.
We also have access to a limited amount of basic gardening tools and mulch. Garden work parties and work groups seem to be common events at a community garden, especially at the start and end of the season. From what I can tell you usually attend these if you are able to and it is a time when everyone works on the garden all at once.
There might be other odd rules too. For example, we have a list of things that we cannot compost that normally you could and there are no trash cans to place trash so we must take it with us. I was also surprised to find out what plants were considered invasive here as some of the plants were things we commonly plant in the Midwest. I don't think you will have a problem with this because you have always lived and gardened in New England.
You must tell me more and check to see if there is a Garden Manager. It is nice that you may be able to fulfill all your green produce needs for your family with this additional space. I have enclosed the following link to the page of rules for the Portland Community Gardens. http://www.portlandonline.com/parks/index.cfm?a=93178&c=39846