I have always played in norwegian (my native language) but with english or swedish books depending on which system we are playing. We tend to translate weapon and monster names into norwegian (at least when they have norwegian equivalents), but use many game terms from english (such as "hit points" or "feats").
Additionally, we have had to learn some of the imperial measurements (feet, inches, miles, pounds) in order to understand the distances and scales. However, I still do not use the weather system from the DMG when I DM, mainly because I have no idea how hot or cold "100 degrees Fahrenheit" (for instance) is.
-- retan