You do know that you have to pay for wifi in general, right? You need a wifi subscription and then pay per minute for usage. But there are a handful of free wifi spots. Check out this website:
www.wififreespot.com.
Have you ever been to Festival Walk in Kowloon Tong? There's free wifi there. Fantastic shopping centre, and they have the biggest Pacific Coffee in HK. Very rellaxed there. They even have like study desks, so it's obviously designed to attract working people to work there for hours on end. Haven't found the need to take my work there, so haven't tested out its wifi and don't know if they allow you to plug the laptop in, but it's a big place and I'm sure there are plug sockets all over.