Cab Availability and Procedure (São Paulo)

I've noticed that many of the theaters and cultural venues are located north of Avenida Paulista, even in Centro. I know Centro can be unsafe at night.
As one leaves the theaters, are there always ample official cabs?

Is it advisable to have your hotel reserve a cab for the time the performance will be over? Are there cab companies that can handle your call in English?

Would really appreciate any recommendations, as I want to enjoy what the city offers, and wouldn't want to be caught in a situation where transit back to my area would be an issue