In Chicago, permit parking is street by street, sometimes block by block. There are winter rules as noted above. Moreover, unpredictable bans arising from "snow routes" in Winter (where parking becomes illegal whenever there is 2"+ snow) and "street cleaning" at other times mean that you can't leave your car unattended for long.

Basically, smaller streets are safer for a quick getaway, but do read every sign on the block. If someone can keep an eye (and move the car if necessary), then you are safe. Otherwise I'd look into paid parking.