I don't listen to much CPD trunking. I imagine it's a little less formal, though I could be very wrong. You are correct werinshades, my lingo description was very general. There's a lot I don't understand, such as RD numbers and events but that's a topic for another thread.
If you don't want to program frequencies, you could do a search of the 460-465 Mhz band to get most of the Chicago Police dispatchers and City-Wides. I don't find listening to Chicago Fire Department very interesting, but that's only my opinion.
Enjoy your stay, midnightcaller. Check out Wildfire Steakhouse on W. Adams St. if you're looking for an awesome (though somewhat pricey) meal.