public transportation to local ski resorts (Santiago de Chile)

hi,

i plan on living in santiago, chile, from june to october. since i will not have access to an automobile, im very interested in finding public transportation options that depart from santiago and arrive in either valle nevado, la parva, or el colorado. ive found some private services, online, however, they seem rather pricey.

does anyone know of any cheap/reliable transportation options from santiago to the local ski resorts?

thanks,

farzad