a cab is the best option! they pick people up along the way which makes the fare cheaper. are you going alone? i shared it with a friend and we found it to be fast and reasonable. we went from santiago to san jose de maipo. i don't remember where we caught it, but do negotiate the price before you get in. it's about 1.5 hrs. are you going to cascada de las animas? we went river rafting there and they had the cutest cabins, a great restaurant with live music and a super fun staff. you should go! we also stayed in a little french guesthouse just nearby. i can dig up the info if you need a place to stay for one night.
here are directions to cascada de animas...
that's the best i can do!
In high season (mid December till Holy Week) there are daily buses departing from San Borja bus terminal (on the western side of Estación Central; go across the shopping mall till the end of it and ask for ‘buses al Cajon del Maipo’) to the tiny mountain village of Baños Morales.They cost CH$ 2000 (US$ 3) one-way per person and take some 3 hours to get to the final destination, 300 metres from the park entrance.
They leave at 730 AM, but since there are just one a day, they’re packed –mostly on Saturdays- and is wise to be there at least at 645 AM to get a seat. The buses return from Baños Morales every day at 600 PM.
There are also minivans (‘Turismontaña’) from the SE side of Plaza Italia, leaving at 800 AM, and which cost CH$ 3500 (US$ 5) per person, arriving to destination at 11 AM or so.
In summer, a private car (non-4WD) can do the trip easily, but be careful at the last stretch of the road, where there’s a steep climb with protruding rocks. After the first snowfalls in autumn, only 4WD’s can do the journey, and in high winter it might be impossible to even reach by land vehicle further from Lo Valdes, 4 km. downhill. If a heavy snowfall happens while you’re there, it’s almost sure that a military or police helicopter would fly up there to collect stranded climbers and take them (for free) to San Jose de Maipo, but don’t rely on this flight if weather is too rough.