Can Descent: Journey in the Dark be played by non-English speakers?
There are two significant challenges to playing Descent in a language that you aren't fluent in.


Text ability on cards (characters, upgrades, monsters, overlord cards, condition cards, etc).  Fantasy Flight Games (the authors of Descent) use very precise wording.  Often particular pieces of linguistic nuance contain information about rules or timing that you can't miss.  For example, Leoric of the Book's ability: "Each monster within 3 spaces of you receives -1 damage on each attack roll (to a minimum of 1)".  Reading this in a language that I is not my first language, I would likely be quite confused as to whether or not this ability affects monsters at range 3 of me (it does) and might misunderstand that the parenthetic is actually an additional constraint on this ability and not just a clarification (it doesn't ever reduce an attack to 0 damage).
The rulebook and adventure book take nuanced text to the next level.  Even reading the rulebook in my native language, I still missed that monsters could only attack once per turn my first game.  There is a lot of information that players need to have in these books.


All of that said, Descent is actually a good game for this because as long as the overlord knows all the rules, players can ask the overlord questions (including about precise translations).  This is because the overlord has total information already, so there is no hidden information that is given away by the question (other than players' plans/intentions).

My recommendation would be to get the game in the primary language of the player you intend to be the overlord (most likely you), and print out the PDF's of the rulebook and adventure book in the other language (these are at least available in English on the Fantasy Flight website).