By Bus -- Getting here by bus is cheap, but takes forever. First you'll need to take the Metro Line 4 toward Puente Alto and get off at the Las Mercedes station. You'll come out on Avenida Concha y Toro, and from here buses pass by every 10 minutes for San Jose de Maipo; if you're headed to San Alfonso, you can take a taxi colectivo (shared black taxis) from San Jose for 75¢ (50p) once you get there.
By Taxi -- This is a faster option than the bus. Take the Metro as stated above; outside the Metro station await the taxis colectivos, which leave every 10 minutes from 7am to 8pm and cost $2 (£1.35) per person. Regular taxis (with the yellow roof) from the Mercedes Metro station can run anywhere from $13 to $19 (£8.70-£12.70) depending on your destination in the Cajón. Always negotiate a price with the driver beforehand.
By Car -- The fastest and easiest way from Las Condes or Providencia is to take Avenida Vespucio Sur and head south until the avenue turns into a highway. Exit at Las Tores and continue straight along the lateral road and make your first left, heading under the freeway. After turning left, get in the right lane and veer right immediately onto Avenida La Florida. Continue along this road for 12km (7 1/2 miles) until you see the road fork at Puente Alto; head left at the sign pointing toward San José de Maipo. If you are downtown, follow Vicuña Mackenna Street until you hit Departamental, and head left (east) until you run into Avenida La Florida. Take a map and count on snarling weekend traffic. If you plan to go to El Morado, note that there is a police checkpoint where drivers are sometimes asked to show their documents, including a passport.