There is one in the West Loop, on Fulton Market, just west of Halsted. It's not far from the United Center if you find yourself over here for a Hawks or Bulls game. There was one in the 'hood, the original in Humboldt Park, but they lost their lease (like 3 months after renovating the hell out of the place and adding value to the landlord's property) and are building out a new space on the west side now. They have a temporary one open at 3129 W Armitage. Also if you're at the United Center it's not far away and it will be a lot easier to find parking around this one than the West Loop one.
Tip: you get three salsas, green, red, and really deep dark red. Deep dark red is where it's at. An earthy, smoky spice that is perfect on the sandwich.
Another tip: they have multiple cemitas. Atomica (above, with all the pork), milanesa, jamon, carne enchilada (those three are the three things that go on the atomica) are best--any sliced meat. They have some offerings like carne asada, pollo, arabe that are pulled/chunked meat, and they tend to fall apart when you eat them on the sesame roll, whereas the first four I mentioned are sliced meats that don't fall out and make a mess when you eat it. If you're in the mood for the arabe (it's really good) it's best on a taco. Stick to the sliced meats on the sandwich.
Edit to add: oh, also. Summer is the best time to go.
That's when papalo is in season.
