A friend once told me that going to Peru and not visiting Cordillera Blanca is like going to Nepal and not visiting the Himalayas. I think I would have to agree with him. The Cordillera Blanca, and the Santa Cruz trek in particular, has been praised as one of the best places for trekking in the world.
Why is the Santa Cruz trek so popular? Well, to start off it is safe and gorgeous, not to 
mention the world’s highest mountain range outside of Asia. The weather is great from May to September, and although the hike reaches an altitude of 15,617 feet, the pass is long and slow, allowing your body to adjust to the changes in altitude. The scenery is gorgeous, with red quenua trees and beautiful mountain lakes.
The normal route is about 31 miles, starts in Huaraz, and 4 days hiking, 3 nights camping are recommended. There are campsites with toilets along the way. A trekking permit for Huascarán National Park, which costs US $20 is currently required, although changing that amount is in the works.
Be careful when finding a guide; oftentimes international companies will overcharge, and unofficial guides will sometimes try to rip you off.
Instead try one of these companies:
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