I made a really cool find the other day:
http://www.floridasurvivalgardening.com/2014/04/can-you-grow-fruit-trees-in-bad-soil.html
Check out the crazy plant communities going on there. It's an abundant woodland edge system on lousy scrubland soil, right at the entrance to a neighborhood.
Now that I know this natural food-producing system is there, I'm living in fear of it getting cleared. I need to look up the lot in the county tax office and see if I can contact the owner.
People are always asking me if you can grow food forests "anywhere." I think the answer is "almost."