Before travel to China, create a throwaway email account on a service, possibly Yahoo. Don't touch your real email accounts while you're there, if possible. The only time I've ever had an email account hacked is following use in China.
My employer (smartly) prohibits bringing any corporate equipment into China - including cell phones which access company email, and generally suggest not touching the Internet (at least any of your accounts) at all.
Having been there, this is honestly very good advice.
I heard Google does that. I work for Microsoft and am based in China, so obviously this is not an option for me. It turns out not to be a problem in practice, everything is encrypted well enough, the only annoying thing are GFW-instigated DOS attacks on secure connections.
Nice thought, but you may not find it easy to access GMail. Yahoo's "tight" relationship with the government means that its site works most of the time, and has usable performance. In China, all web sites are not created equally. Rather than outright blocking, the general strategy appears to be to kill the performance of sites, raising frustration.
