I dob't think signs keep anyone out, but then they don't hurt. I also live in Illinois and I obtained from the state fishing guys a supply of about 4 x 5 inch cards that you have tresspassers you do allow (friends, neighbors, your banker) sign that basically give them tresspass permission. When they sign it is a release of liability for everything but intentional harm. It is a perforated form that you keep part of.
My game warden adivsed I should put a purpose for the tresspass and an end date. As an example a high school buddy asked permission to mushroom hunt. I filled out the purpose to be "mushoom hunting in season" I dated it to end 12/31 of that year, I told him my insurance required an end date, then when he approached me for the next year I did it again.
I also "manage" some land held by my mother in trust. In that case I advise them to always carry it with them when they are on the land. That way, if someone challenges why they are on the land the card is their permission to be there.
Bing
