Terry,
Since I'm a bad boy we always did it then saw what happened. We never once got any flak from forest preserves or park districts. I'm not saying to do it and I think working with them is good. Try to impress upon them that the IDNR paid for some of these and their logo is on the sign. I believe that having the IDNR logo on there keeps FP and PD from taking them down. Basically it's like an approval from the IDNR. We have signs in the PD and FP in Naperville (which some people think is _____ town) and if they let them stay I think that's a good sign.