Entrance is at the back of the lot.
There is a little fireroad, but not enough to ruin it. Take the main trail to the left of the parking lot and the main trail will empty into a single track lane. You're there, dude. It eliminates having to cut through the main path in Cutler Park but there's always the risk of the State Police getting funny with your vehicle parked there. My fear is that by doing this it'd be majorly overrun, but it seems like a worthwhile chance to take rather than push the generosity of the MDC any further.