The Train Company of Sao Paulo (CPTM) offers three different day trips from Luz Station in downtown. They are all nice, but this might be the best option if you want a quick get away from the city. You can buy the tickets at the station and they leave early on some weekends (you better check their calendar before you schedule this trip). The old train is a tour in Sao Paulo's history and the trip at Paranapiacaba (or Jundiai and Mogi das Cruzes) can be arranged with a few agencies that work in partnership with the CPTM.
Paranapiacaba, Santo André - SP, 09150-100, Brazil