Traveling to Chicago Question?

Hey I'm wanting to go to Chicago and little after Christmas as I want to become a Police Officer at the CPD and have never been there. I am only 18 and I have two years before I need to know the area of Chicago. My question is 1) I've never driven in any large traffic situations, what will the traffic in Chicago be like during the daytime? (I plan on leaving around 2-3 A.M) 2) What's better, driving or walking in the city of Chicago? 3) Is there anything else I should prepare myself for to take a trip there? There's not really a reason I want to go there other than to attempt to find my way around to be a Police Officer there in a couple years. Thanks.