I agree with the other responses, although in the past three years I've had my permit checked only three or four times. If you use the park without one you definitely do so at your own risk.
If you go to the DuPage County facility, in Wheaton, they can give you a one day pass. Or you might be able to do it online. Or you can purchase a pass right now for $20 for the rest of the year. If you are a resident of DuPage County the fee is only $40 for entire year. There are several Parks you can go to in DuPage County, not all of them fenced-in. There's a map at the beginning of every dog park. I've been taking my dogs to the park their entire lives, they're very strong and healthy.Dont go without anything, fines used to be $75 now there up to $150
At this point a day pass is the same price as a yearly pass since it's ½ price after September -December 31st. You can go and check it out one day but that's a park the rangers patrol a bit more. If you go on a Wednesday and it's crappy out the rangers are MUCH less likely to be there. FYI it's a 75 dollar fine.
Thanks! Your answer is awaiting moderation.