If you absolutely have to send text messages on the move (via cell-phone), I know of no cheap way to do that. But text messaging via Yahoo isn’t blocked in China. You can also make cheap calls via Skype - quality can be pretty decent, depending on your broadband provider.
Thanks; what about AOL Instant Messenger, either via the client software or via the web interface, AIM Express www.aim.com? Can someone who is in China use either version of AIM? Thanks.