Yes I have been to Chang Ping, Guangzhou and Shenzhen recently.
It really depends on where you log in from. Some sites are blocked, some are'nt. It is mostly the most well known porn sites that are blocked.
You should definitely have a proxy to log in with. But that is not to say that the connection you are logging in with is not monitoring your surfing activities.
It is possible a porn site is NOT blocked the first time you go to, but then after it will be blocked.
Google:
Golden Shield Project