This new bus service is being encouraged by hotel operators in CSL:
http://www.rutadeldesierto.travel/english/
They run from about 5 AM to 11 PM, every 10-15 minutes, and seem to accommodate a fair bit of luggage. BTW, one stop in San Jose is at the Comer (formerly Mega) Supermarket, which is almost as good as Costco as a place to stock up on supplies)