Temperature gauge stuck on C. Rarely goes to mid. A/C sometimes does not blow cold air. Also I wanted to know if driving with the cruise control button on with out actually setting any speed?

If I understand your questions, the cruise control button can be in the on position without setting it on auto cruise. Only when you place in a desired speed you want to "cruise" in will it become activated. The control button, is it a roll type device or a knob you turn? Sounds like you have something mechanical sticking, a wire leading to one of the heater doors? Yes check with the dealership to see f they have beeen having any issues with that type of control device before and what the fix is. A good service rep should beable to tell you what the problem may be, if it is covered under warranty, (GM will pay the dealership to fix it so they get their money no matter who pays) or if it is not covered and the cost to fix it.

Then control button is just a button, not a knob or such, ... Thanks guys!!