I wouldn't mind a game set in China, as long as the voices are all in Chinese and most texts around the world is in Chinese.
I know most of us won't be able to read it but so be it.
If it's set in China then the language should be Chinese, not English.
Then of course there'd be some chinese who knows english, and probably decendants of american soldiers who were in China at the time of the Great War and survived, or they're ghouls. Maybe many of these soldiers got into cover when the bombs fell, some kind of chinese vault maybe that they had siezed, and maybe not everyone retreated there in time so they had to lock some of their friends out. Then the bombs dropped over China, many of these soldiers died in the blast, many died of radiation poisoning, but some... some turned into ghouls. And they wanted revenge on their superiors who left them outside that vault. These ghouls, with combat armor (even some power armor) and a good arsenal of weapons created a faction, and to it they gathered chinese survivors of the firestorm. Later on, the US soldier decendants open up their vault, to face these revengeful ghouls and their little chinese army. Of course, the humans the ghouls wanted revenge on are long gone.
But really, if everyone would be speaking chinese, then this game would be inpossible for anyone to play except the chinese (and I don't know how much they'd like a game taking place in their bombed-out home country, and it probably will br alot of ingame references that China might be offended by somehow (like how Japan didn't like the nuke in Megaton). So there'd have to be people speaking english. This faction with american ghouls as leaders would probably have learnt their chinese followers english to some degree. And maybe there could be a perk you could take or gain, which makes you understand chinese (that is, the subtitles would show up english but the NPC still speaks his own language)