The manual I have says to take the bumper off to access the fog lights to change a bulb.

I got access by removing the mud guard in the wheel well behind it. There seems to be a single nut holding the assembly in place, but it's rusted solid.

Is there another way to change a fog light bulb, or something I'm missing?

 

u should be able to pull the bulb out only, without having to remove the light assembly... just follow the wires, it should head to the back of the lamp.