Starbucks has free internet in Guangzhou. Also, next to starbucks in Zhujiang Sincheng is Cafe Dilettante which has better coffee and free internet, and ample power.
As far as I know every Starbucks could provide Free Wi-Fi service.
You can detect the Wi-Fi signal which is call "CMCC" in most place, but it is not for free.
Most hotels provide free internet connection in room.
try xindanwei.com, it's nearly free
Good option is Gails Place - decent food, great sangria, excellent selections (http://gailsplace2000.com/)
Free internet, used book swap, and staff speaks English.
I go there all the time