I wouldn't rent a car, unless there is some place that you feel you MUST go to which is not near public transportation. Too expensive for the rental and for parking, and too inconvenient. And you don't need it; there's plenty within walking distance of the Fairmont, and the rest of Chicago is easy to get to on the CTA (els - that's our subway, some of which is elevated - and buses). Check out the information on their website at
transitchicago.com.
As for your choices, it sounds like you're considering a lot of places that are not all that different from what you have at home in Toronto. Blackbird, Nightwood, and Avec all serve food that falls under the general category of "contemporary American", and you can get similar food at home. I think Mexican food, recommended above, is a great suggestion - in particular, our provincial Mexican places, which are so very UNlike the conventional tacos/enchiladas served in most cities this side of the Mexican border. Check out the menus on the websites for
Mundial Cocina Mestiza,
Mexique, and
Mixteco Grill to get a better understanding of how their cuisine differs from the ordinary. (Mundial is a block from the 18th Street station on the CTA Pink Line; Mixteco Grill is three short blocks from the Montrose station on the CTA Brown Line; Mexique is on Chicago Avenue which the #66 CTA bus runs along.) Rick Bayless's Frontera Grill and Topolobampo, which are a 10-15 minute walk from the Fairmont, also fall into this category; however, unless you can arrive at Frontera before they open the doors, the excessive waiting times there (and the impossibility of getting last-minute reservations at Topolobampo) make those places impractical. His Xoco just does not compare for creative cuisine, IMHO (again, the differences are easy to see by checking out the website menus).
I would also get some authentic deep-dish pizza, our delicious local specialty for which Chicago is so well known. The original locations of Uno and Due, where it all started, are about a ten-minute walk from the Fairmont. Lou Malnati's and Pizano's both have several locations around the greater downtown area (although not as close to the Fairmont as Uno/Due) and also serve terrific versions of deep-dish.
Regarding reservations, rather than assuming you can't get them, why not try making them now? Most of our upscale restaurants accept reservations on Opentable.com where you can see at a glance which ones have availability for any given date and time. (If an Opentable restaurant shows no availability, you can
sometimes still make one by calling the restaurant, but don't get your hopes up, especially with popular places like Topolobampo and Girl & the Goat.) Of the places I've mentioned, Mundial, Mexique, and Topolobampo accept reservations on Opentable; Mixteco does so but only over the phone. The pizza places don't take reservations, although you can accomplish the same thing at Malnati's and Pizano's by phoning in your pizza order in advance; they'll seat you right away if you have a pizza coming out of the oven shortly after you arrive.