It sounds like a really great area! I'm fortunate enough to come from a spot in NJ that isn't much different from what you are describing...wild berries galore! Not only do the box turtles thrive on the berries, but the fruits attract insects that may become part of the box turtles' diets. You'll have to watch for nesting behavior. If you live in an area with dense woodlands and/or vegetation, the turtles often choose open yards in which to nest.
That is interesting to hear about how social they are. Perhaps there is a friendly "hand feeder" somewhere in your neighborhood. It wouldn't be the first.
I'm still hoping for pictures.