OK, it was hard to tell exactly what you meant by Chicago, and Chicago Metro area. Right downtown it can lose the satellites easily. But it can also lose them outside the city, a well. One thing you have to remember is that GPS signal are nothing more than radio signals, and lots of things can interrupt the signals. If your GPS unit shows them, or if you have an application that shows all of the possible satellites, you can see which ones the unit is connected to and how strong the signal is. I have an Android app called "GPS Test" which gives a good visual of signal strength and connected satellites. The civilian GPS uses a single frequency, while the military GPS uses two. The single-frequency of civilian GPS makes it more vulnerable to signal degradation and loss by a host of factors, not the least of which are natural interference and the quality of the GPS receiver electronics.
As for the government jamming GPS signals, just like any radio signal, it can be jammed. But it's highly illegal to do so, even by the government. It's also insane, since jamming GPS signals dramatically affects aircraft and shipping navigation. Not really something you'd want to do in and around Chicago. Too many businesses rely on it, plus the E-911 depends on it. If you want to disrupt G8 Summit protesters, jamming GPS won't have much of an effect, since intersection street names can be quickly Tweeted. Far more effective to block social media than to block GPS.
In the last couple of weeks we've seen the results of increased solar activity, which has affected GPS and satellite radio at times, briefly. This Saturday and Sunday (Feb 11 and 12) we'll get hit with the results of a couple of really large solar flares, which could render GPS units useless for short and long periods of time. On Monday and Tuesday, for example, three large solar flares and several smaller ones erupted from the Sun and started hitting the Earth on Thursday and Friday, causing GPS and other satellite problems. Should make for some nice North and South Pole light shows, though. Look for more episodes this weekend especially, and throughout next week. The Sun has gone from a relatively quiet period to a relatively active period, and should remain active for a while, several weeks to several months. On a scale of 1-5, with 5 being strong enough to knock out power grids of cities and countries, what we're seeing now is about a 2 or a 3, which is enough to mess with GPS and other satellites for short periods of time, assuming it doesn't fry any of the satellites.
