As they said the Forest Preserve is a people friendly area. I am sure it is large and wild, but they are frequented by many people. Not all are ganja bandits looking for someones grow, some are "Just say No" and will do their civic duty if required.
Try and find a few isolated spots, put 1-2 plants per site about 4' apart from each other. When going to visit a site bring an alibi, mushroom hunting, bird watching, walking the dog, or anything similar incase you are asked.