First check the thermostat by letting the car warm up at idle, check for a temperature difference between the upper and lower hoses when the car warms to operating temp.

Another important thing to note is that if your coolant mixture is too lean (50/50 is good for this region) it can cause overheating due to the water boiling and putting air into the system.

Then drive the car, when the car gets hot, check to make sure that the cooling system is holding pressure. Lightly squeeze the upper radiator hose, it should feel like it is pressurized. If it is not pressurized then you have a pressure leak somewhere (radiator cap is likely).

If it is holding pressure, not overflowing into the overflow container, your thermostat is opening, and you have a 50/50 mix of coolant/water, and your car is still overheating then you have a problem.

One more thing that is important, your car should not overheat while driving at highway speeds even with your fan off because you are pushing more air across the fins than your fan could ever hope to. This is a valuable piece of info.