There is no direct road south from Valparaíso [1], but the paved road west-southwest from the Casablanca valley passes through a series of popular beachfront towns. Regular bus service from Valparaíso [1] is with Pullman Bus Lago Peñuelas, and from Santiago [2] with several companies.
Links:
[1] http://www.moon.com/destinations/chile/-chilean-heartland/valparaiso
[2] http://www.moon.com/destinations/chile/santiago-and-vicinity