Some guidebooks are wrong, they now charge US$10 (80 bol) from Extranjeros (locals/local students pay 10/3 bol). Getting there is easy. Catch a bus/micro from the cemetery area of La Paz - expect a 90 minute drive, and expect to spend half the time picking up more passengers and escaping the traffic of El Alto. Price: 8 bs. You can also book a tour through the many tour operators in La Paz. Most of these appear to be in Spanish only.
The remains of a Pre-Incan civilization, the last skeleton recovered was 13,000 years old, this place is quite magical.