Origin is a great WiFi cafe with good internet, brilliant coffee and a lot of space around. If you want to work for longer in Cape Town then I recommend Greenpoint coworking.
Best coworking space in cape town with fast Internet, great coffee, telephone booths and you can use meeting rooms without any extra charge. There's also 24/7 access if you work odd hours.
Field office is one of the best wifi cafe in Cape Town with free wifi, amazing coffee, friendly staff and beautiful set up. A casual work space to take your laptop and perhaps meet some hip creative people.