Post in Puente Alto, Santiago Metropolitan, Chile

Me and 4 friends (couchsurfers) are staying at a rental in San Alfonso/San Jose del Maipo. We'll arrive Christmas Day (25.12.17) but several bookings don't offer food nearby. Is there a street market (for groceries) or a grocery market open in Santiago or the San Alfonso area where we can stock up on some food to cook for ourselves in our rental? or some good local restaurants or a couchsurfer's potluck for us to try/join? We'd appreciate some local interaction.