I would imagine you could plant strawberries, depending on how much soil you can get to you might be able to plant onion and garlic. You could also do a search or call your local Master Gardener office and ask what grows in the wild and plant that. You might even be able to get away with some blueberries or tomatoes?.
Good luck and have fun.

Great idea!

Are you planning on harvesting the edibles? And how often would you be able to work on the spot?

If you're not going to be there regularly, I would think most edibles would be a deer magnet.

You could try some kind of bramble fruit (blackberries, raspberries). Could be a little spendy, tho' which is often not something you want with guerilla gardening. Most edibles require better soil and more consistent water. But a lot of herbs do well in rocky, dry soil. Think Mediterranean plants like thyme, savory and lavender.

As far as ornamentals go, you could have great success with sedums. They love that kind of site, and they will spread and choke out a lot of weeds in the process. They come in an incredible range of shapes, sizees and colors, and it's always kindaa nice to walk by and think "*I* planted that blazing mound of gold, and that patch of blood red creepers!"

Good luck!

thyme