San Agustín de Valle Fértil
Vallecito bus company has three busses a day from San Juan, departing at 7:30 (Mon-Sat), 14:00 (daily), and 19:15 (daily). The cost is 162 pesos.
The Ischigualasto National Park (Moon Valley) and the Talampaya National Park (canyon) are nearby. Two tourist companies can take you there (they will wait for you at the bus station); note that the entrance fee to the parks is not included in their prices. The HI hostel also takes your to the parks.
Vallecito has three busses a day to San Juan. They depart at 14:00 and 17:00. Monday to Saturday there is also a bus at 3:30am. The price is 96 pesos.