I'm not aware of how Create a World works or is installed, but can there be something similar to this thread where it is explained how to change your game's language?
Could be. But I am not really sure of that Create a World will take the language from the already installed game, or from the account that is created at
www.thesims3.com, and therefore the given country the member lives in.
For now I am running it in Dutch, which is a bit of a pain in the you-know-where, because of the constantly required translation to the tutorial and vice versa. But anyway, it works however, so maybe I just need to stop complaining.
By the way, it is a wonderful and user friendly program once you know how to handle it. You should definitely give it a try.