From downtown, take a cab (one way will be less than $10) or drive west on I290, exit on Ashland and head south a few blocks to 16th. Now check-out the wall on the north side of 16th street. EEK!
Now just head west along the wall (in your car/taxi: it’s not a very nice walk) and enjoy the some of the finest street art in the city.
Chicago's Best Murals & Street Art: http://bit.ly/17Dkgbt