Eileen is interested in VPN services when she goes to China. Leo says that in many cases, the Chinese government will block VPNs and in some cases, it could put up a red flag. Leo spent a few weeks in China a few years back and access to different social media comes and goes. There's a great Wikipedia Page which lists what works and what doesn't. Another good one is GreatFire.org.
(Disclaimer: ProXPN is a sponsor).