Originally Posted by
Peter_N-H
Possibly the noisiest city in China, which is saying something, and although not without its attractions, offers the least of the major metropolises for the effort put in. Even if this is your only chance to go to mainland China, there are other side-trips from Hong Kong more worth your time: Kaiping, for instance. But better, if you think you may one day return, to save your efforts for another longer trip in the future. I'd second the suggestion of Macau for now. No visa needed.
I agree with Peter, there are better day trips into the PRC available if that is what you are looking for.
Guangzhou is truly a business city and I wouldn't recommend for a tourist visit, especially if you don't already have a visa. If making a list of must-see cities in China, Guangzhou and Shenzhen would be pretty far down!