I think it depends on the film and the nationality. Nobody except a real clever-clogs would use the original title of a Japanese film. For more common languages like French and German, it just depends. There are some films where, I think, you would always use the original title- for example- "Les Enfants du Paradis". With others, you would use the English translation- for example, "The Wages of Fear". Usually I just point at the poster and say "that one" (and end up sitting through "Barnie's Big Adventure" instead of the one I really wanted thanks to a misunderstanding with the ticket seller).