Buses to Pisac leave daily from Avenidas Tullumayo and Garcilazo, departing whenever they have enough passengers, which is usually about every 15 minutes. It's approximately a 45 minute ride, costing around $1, and you will be dropped off on the edge of town, a few blocks from Pisac's main square. Go back to the same spot to take a bus returning to Cusco, or to head on to Urubamba and other towns. If you don't mind spending a little more, a private taxi can take you to Pisac from Cusco or back for around $10-13 one-way (25 to 35 soles, up to four passengers). Alternatively, there are also chartered bus tours which can be arranged through any travel agency.