Here in Australia I find mulberries and macadamia nuts in a nearby abandoned garden. Passion fruit grows wild sometimes too, and is easy to grow in a home garden, as is paw paw. You can drink the nectar from some tropical flowers if you have the patience!(A gardener at the Roma Street Parklands in Brisbane showed us - he was always having this little sweet snack himself) Also, loads of weeds are available for my chickens: English plantain, any dandelion relative, wild purslane, and of course chickweed are the best.
I'm thinking of doing a bit of guerilla gardening - dropping pumpkin seeds etc around the grassy byways. You can wrap seeds in balls of clay/mud, let them dry, then throw them where you want them to grow. They germinate (hopefully) when it rains.
Back in England as a young 'un it was blackberries, mushrooms and crab apples. As kids we also ate the spherical bit under the purple thistle flower, and took nettles home to Mum for soup, though she did not appreciate this, being always rushed off her feet.
Once I found some Caribbean gherkins growing wild near a grassy footpath near here, but didn't recognise them as food. They have disappeared now.
Passports not in the drawer I always keep them in. Turning the place upside down.