Agencies usually translate your English keywords to foreign languages automatically, using automatic translation systems.
There are some exceptions such as Fotolia, where you can choose in what language you supply your keywords.
But I suggest you to use English keywords mostly, and use foreign keywords only as addition to English keywords. Such as use them for geographic names (mountains, etc.), names of cultural heritage (castles, museums, historical locations, etc.), simply for those that do not translate to English at all, or their non-English names are popular in country of their origin, thus it is likely buyers will use non-English keywords when trying to find them.