You may be able to grow potatoes on Mars, but growing them in the Andes doesn't really get you that much closer to Martian conditions.

Average pressure on Mars is about 0.6 kpa which is a trifle less than the pressure at Cusco which is approx 65 kpa pascals. Mt Everest is still about 37 kpa.

I believe you'd have to go about 50km above sea level to hit the average pressure of Mars.