This seems like a pretty good book, I bought the one I linked above, but reading isn't really my thing. I learn better through seeing.
I would strongly recommend downloading all the videos as well as Xcode 4.2 before you leave for China. The files are quite large and I hear it's a long plane ride. Sign up for the iOS developer program if you have not already - you can't build to your device otherwise. 
Feel free to shoot me an email (contact in profile) if you get stuck on something - I might be able to point you in the right direction.
Finally, learning to program iOS apps may not be your best use of time on a trip to China. Even if you are able to go often catching up with what is going on generally and what people are doing/using in the mobile space is probably a better use of your time while there. I know I would not be writing code if was able to take that trip and perhaps even speak the language.
 http://www.amazon.com/Programming-Objective-C-3rd-Developers... (Maybe the kindle edition for reading on your laptop/iPad)
Fresh book recommendations delivered straight to your inbox every Thursday.