You should install localized versions of Office 2010 suites for one language and one or more Office Language Packs 2010 or the Office Multi-Language Pack 2010.
Localized versions of the Office 2010 suites
Licensing localized versions of the Office 2010 suites (such as Office 2010 suites in English and Office 2010 suites in Spanish) may be best if your organization needs completely localized functionality and the additional content that comes with some fully localized versions. Each localized version includes at least two sets of appropriate proofing tools for the languages you're likely to use most (for instance, the Norwegian version includes Norwegian, German, and English proofing tools). To expand advanced editing and UI support to up to 37 additional languages, you can add one or more Office Language Packs 2010.