Reading this whole thread, I was struck with one question, "What is the main thing you want these signs to do?"
Do you want to tell people how to grow these plants themselves, ie sun requirements, moisture requirements etc. This is information on seed packets or nursery tags.
If you want to teach people about what plants functional roles are in the food forest then stick with those symbols or words. This would be a great way to teach people about the whole concept of a food forest.
If you add an additional layer such as human uses for the plant then that's ok.
But, you need to figure out what information you are trying to convey then stick with that on every sign. Keep it as simple as possible or your signage will be bog most people down.
Plant geeks like me can look up the latin name and delve into growing it and using it ourselves. Or offer the QR code as a way to get more in depth information on everything but the permaculture function in the food forest.