In (American) English "at the front" is quite common. "In the front" is also common. The difference between "at" and "in" is based on the location of the object/person with respect to the area within which it/he is located -- He is in the front of the car. --> He is **inside** the car and is seated in the front seat. He is at the front of the car. --> He is **outside** the car and is positioned at or near the front of the car.

To me, there could be subtle difference. 'at the front' could mean sitting on the bonnet of the car. But that's a bit silly in your example, so they are probably the same. In some cases, they could be different. e.g. you would say you had a decoration at (or on) the front of your car. 'in' makes it clear that the thing is inside, not somewhere else near the front.

Thank you Teacher Adam

In regards to your example, only using "in the front" is natural for the context. In fact, "at the front" is rarely used, other than when describing the location of something within a shop.