I have been to Mario's cafe 2-3 times in the last year. The food is an interesting mix of Germanic and Middle Easter/Greek cuisine. Their salads (bean and cabbage) use garlic/lemon juice/oil for dressing, they have their own version of Kefta/keftades and they also have some type of sausage casserole which I will try on my next visit.
For apetizers, make sure to try the fried zucchini and the shorba (garlicy yogurt), they also have an eggplant salad which reminded me of Baba Ghanouj without the tahini.
I have already tried their Kefta and paneed kashkaval (a strong yellow cheese made from sheep milk), and they were both heavy, stick to your ribs type of food, yet excellent.
They also have some good choices of inexpensive bulgarian wines. I'd highly recommend giving Mario a try on the way to drop someone off, or after picking up someone at O'Hare. It's not that far from the Harlem exit.