The nearest coffee shop to the con hotel is Caribou Coffee at 41 E. 8th Street -- that's just around the corner from the hotel, a 0.2 mile walk according to Google Maps. The next closest is a Dunkin' Donuts at 600 S. Wabash Steet -- also very close.
I plotted these on a Google Map, which I think you should be about to view HERE. ::crosses fingers and hopes that link works::