Depending on which countries you'll be visiting, you may not need to do any translation as many caches already include an English version of the description and clues.
If that's not the case, I second what abiherts said - google translate is a good enough tool if you have access to it while geocaching. Otherwise there are apps for smartphones that translate texts into English. The translated text will sound a bit funny, but it's usually good enough to be intelligible.