Cuzco Peru altitude sickness?

3,300 meters (10,800 ft) http://en.wikipedia.org/wiki/Cuzco

Altitude sickness reduces the amount of oxygen in the brain, causing such symptoms as dizziness, shortness of breath, and mental confusion

It depends. You might get it or not. Some people are never altitude sick. Some are, when they are already on the altitude of few meters from the ground.

The lowest recorded case of serious altitude sickness (HAPE) was at 2500m in a climber in Japan. However, most people need to travel above 3000m and stay there for at least 12 hours before symptoms...

11,600 feet. See the related link for more information.