You will want to figure out where you will put the planter, and learn about the plants before you adopt them.
Choose plants that can do well in 3 gallon containers for several years. Learn about the fertilizing needs, and soil type. Identify where you would like to put your planter, and select plants that will do well in that space.
For public spaces in California, ever-bearing strawberries are particularly good as public fruit, since they fruit for most of the year. Lemons fruit year round, and some blueberry varieties will maintain green foliage all year.
Dwarf trees and bushes are good options to look into.
It is true that the plant will not grow to full size or produce large quantities of fruit (though you might be able to get several pounds of lemons and a pint or so of blueberries from one plant if well-cared for.)
Productivity is not really the point of the Fruit Fence planters. The point is to grow more fruit in public view, and provide a way for people with less access to soil a way to care for a fruiting plant. Living with a plant for an extended period of time, at home or in your neighborhood, will allow those who get to know the plant to become more attuned with the cycles and seasons of fruit plants. This helps with general appreciation of fruit production.
The plants themselves are almost a form of bonsai plant, you can maintain them at a smaller size and they can fruit. For example, according to internet legend, there was once a 1-foot tall Ponderosa lemon that produced a single 1-pound lemon. The book Pruning & Training
will teach you what you need to know.
In urban environments, you need to pay special attention to places that are windy, or are blocked from sun for part of the day because of buildings.
A roll of 10 yards Tyvek is about $80 shipped from Pennsylvania. We were not able to find other suppliers, but you can contact local printers who use Tyvek, or look on Craigslist and Ebay for extra rolls that people are not using. This will allow you to make about 10 bags.
You'll also want soil, fertilizers, and high quality plants.
If you can, share rides to go to a good nursery and pick up plants. A large bag of soil weights about 50 pounds but can be hauled with a bike if necessary.
For moving the planters around, it is helpful to put them in a reusable grocery bag. If the water reservoir is damp, you might want to bring a towel with you if your bag art is a little delicate. (As is the case if you print onto Tyvek with an inkjet printer.)