Earth's GPS satellites use earthward facing directional antennas, and even on Earth the signal is several dB below the noise floor, so our receivers have to use process gain to actually get anything useful out of them.
Mars is fifty million kilometers away. A GPS reliever on Mars looking for Earth satellites wouldn't be able to hear anything.
Mars is 140 million miles away from earth on average. Even if you could detect signals from GPS satellites on earth they would all be at a single point in the sky.
However, that does bring up an interesting idea. Maybe rovers could navigate using the position of the stars? It doesn't require you to launch 4+ GPS satellites into martian orbit.
I don't see why not - automatic celestial nagivation systems are already a thing on earth, you basically have a system that uses a camera to look at the sky and it gives you an accurate position - most military planes use it as backup in case GPS ever goes down.
Mars is fifty million kilometers away. A GPS reliever on Mars looking for Earth satellites wouldn't be able to hear anything.