If you can't make it to Kartchner Caverns you could give Colossal Cave a try.
You could check out the Romero Ruins in Catalina State Park.
The Pima Air and Space Museum is a nice place to visit. You may even be able to get a tour of the boneyard at the air force base. You could also visit the Titan Missile Museum south of Tucson.
Most of the Mexican restaurants I've tried around here are good. I can't remember the last time I was disappointed.