Does the radiator even get hot? If it doesn't, the thermostat it stuck as people have said. This will stop the fans coming on, as the switch measures the temperature in the radiator, and as the radiator is cold, the fans don't turn on.
However,
Something is suspicious about the fans not running with the aircon on? Do they not run at all, or do they keep turning on and off? They are supposed to have 2 speeds. When you turn the ac on, they should come on at the slow speed. If the slow speed doesn't work however (Blown resistors in fan), the high speed mode will turn on and off instead.
If the fans don't do anything at all, it could either be the fan controller which is goosed, or the fans themselves are dead, but I can't imagine both going at the same time. Try applying 12v directly to the fan and see if they run, and make sure you can turn them by hand to be sure they're not seized.
Back to the thermostat idea though - Does the engine overheat when the car is moving? If the thermostat was stuck, I would expect the engine to overheat even when moving, as the radiator wouldn't be cooling down the coolant at all.