It is easy enough to organise a taxi in Huaraz to take you to Hatun Machay, around 120 soles one way. Once there, the administrator can book a taxi back for you.
A local company "Andean Kingdom" (http://www.andeankingdom.com/) organizes a daily bus trips to and from the crag from Huaraz costing 25 Sols (10 USD) for each way for each person.
There is a modern hut with full kitchen and hot water located a 5min walk from the crag for 30 Sols (12USD) per night. You need to bring your own food, however beer is available at the hut. UPDATE: As of July 2019, the hut is burnt out. There is no kitchen, but running water and flush toilets are available.