In the middle of the CBD the options are a lot, and you might get lost before finding a right place. I found this place in Equitable plaza, and since they had a wifi connection I gave it a try.
The place is small and there are only a couple of tables outside, but they are very large, so you can fit comfortably with your laptop. The real problem comes when you open your laptop and connect to the wifi. The connection is poor and not reliable.
At least the food was really good. I would avoid this place if you are looking to work for a long time, but I suggest you to come at least to try the focaccia (Fugazza in dialect).