I also live a mere block or so away from your new employer and I would have to heartily second many of the recommendations made so far. I especially love the paninis and gelato at Ventrella's on Damen and the simple and cheap wraps at Taste of Lebanon. And if Wikstrom's ever opens again, it has been one of my favorite places to grab a cheap sandwich. (On a side note, if the person who ran Erickson's had some gumption, they would buy some mustard and a loaf of bread and give the people of Andersonville what they really want--a good sandwich at lunchtime!)
But tonight I visited the Fajita Grill at Foster and Paulina with some friends and I would have to recommend it as well. From the looks of it, they have a pretty decent lunch menu complete with chilaquiles and some items off their dinner menu. Tonight I had the combination plate which included an enchilada in salsa verde, a taco, and a flauta. The dishes were prepared simply and well, but the flauta was my least favorite thing, because it was overfried and the steak was downright crispy. But I would have to say that my favorite part of the dining experience was the salsa woman who wheeled a cart to our table and asked us if we wanted red or green salsa, and medium or hot. She then proceeded to mix the ingredients before our eyes with a mortar and pestle and voila, instant salsa!
The ingredients were fresh, my friends seemed to enjoy their namesake specialty, and the service was warm and friendly. I have to say that I will be back, seeing that it is down the street from my apartment. They are BYOB, and I've heard that you can bring your own tequila and they'll mix it into their margaritas. Or should we we call them BYOT? Whatever it is, I say muy bueno!
I found a menu online at the Chicago Reader:
http://www.chicagoreader.com/cgi-bin/rrr/restaurant-menus.cgi?/advertisers//3608.html
Fajita Grill
1708 W Foster Ave
(773) 784-7455