Duo is not the word for two in Spanish. Perhaps Italian, but definitely not Spanish.
The first place I hit when I get to Chicago is Portillo's - best hot dog, hands down. You must get it fully-loaded, Chicago style. Fine dining it isn't, but it is TASTY!
For pizza, don't mess with Giordano's (but if you want deep dish DO go to Lou Malnati's), go to Chicago Pizza and Oven Grinder's (CPOG). I promise you it's the best pizza in the U.S. Nothing fancy or overpriced - just a wonderful pizza pot pie. Sounds strange - but a must try.
For pasta go to Tuscany.
For Greek go to Athena in Greektown.
Be sure to hit Sweet Mandy B's if you have a sweet tooth (best cupcakes) or Scooter's and try a delicious custard/italian ice parfait or a milkshake.