Cobbys does have really good samiches, if you get a large it will probably last most of your stay. The Stage Coach Inn is an old fashion meat and tater place not too far from the fair grounds. In the same area there is the Ranch Club and another location of Chapala. I took a look at the neighborhood of the Expo center on the way to an appointment the other day, across Chinden and/or Glenwood a bunch of places. Sharis (kinda of an Elmers/Perkins like regional chain), Arbbys, McDonalds, Carl Jr., and probably a couple more Im forgetting. There is also a Chinese something Wok place and Chapala's, Casa Mexico and maybe another Mexican place (El Gio Grio?) by Dairy Queen. As bhyde said Sockeye is not too far, a bit further afield is Harrison Hollow another brewery and restaurant. Further west out Chinden in Lindys Steak House and the Nut House a sports bar, havent been to either for a long time. For local flavor there are some old school drive inns, West Side on State St., Fancy Freeze, Hawkins Pack Out, Big Bun, etc.
If you take your meat fried try finger stakes, probably close as we get to a local delicacy. I know the West Side, Big Bun, and Quinns and Tablerock all have good homemade ones. Ask and avoid the frozen ones, they are an abomination.
Todd