Santa Semente has a great feel surrounding it with the 'homely' approach provided by Luke & Sheila. They look after you (including providing a very tasty breakfast each morning), offer advice and keep you up-to-date on relevant local news, etc. The hostel is very clean and well maintained, although you may experience a cold shower! It is tucked away which makes it difficult for taxi drivers to find and is close to a favela, but there is no threat to your safety. A hostel I would recommend.
Despite being out in Meier, the hostel's location is good. Similarly, the staff were helpful and keen to assist wherever they could (helping me attend the police station to acquire a police report for my stolen phone being the best example) which enhances the atmosphere. The rooms were fine, although the bathrooms could have been cleaner/better maintained. Also, there was nothing to stop anyone walking into the hostel and with no room keys or lockers, you had to be careful with any valuables.
Tah! Hostel is a great place to stay in Sao Paulo. It's close to a Metro station, which is easy to get around the city on. The staff are friendly and excellent and helping you out with someone on duty throughout the night to allow you back into the hostel should you end up partying! The rooms are suitably spacious and bathrooms are generally available when you needed them. Be sure to make use of the lockers as some rooms you go through another to reach them. But excellent value for money.