How Do I Change The Language Of My Mac?
To update the language in Mac OS X, go to the Language & Text panel in System Preferences. You can access the System Preferences by clicking on the Apple menu at the top left of the screen. Once in the Language & Text panel select the Language tab, a list of languages will appear on the left side. Note: any changes will not taken effect until the next time you log in.
You can also change your Region by selecting the Formats tab or choose a new input method by selecting the Input Sources tab.