The fog on the windshield could possibility indicate you have a small leak in your heater core. If its on the outside of the window and the ac is blowing cold that's just normal condensation.

The fans kick on pretty high, around 212-215 I think. If the temps drop after fans come on I wouldn't worry about it that much. If you have high mile age and haven't done a water pump I probably would. Its not a hard job and cheap insurance.