Heavy Rain will be fully voice acted in 13 languages, with subtitles also available for all spoken languages, plus five more languages. This info was mentioned this afternoon at Gamescon, when Quantic Dream founder David Cage introduced Pascal Langdale, the actor playing the English-speaking version of Heavy Rain's Ethan Mars (Ethan is the main protagonist), and talked about the extensive voice work necessary for the game's many, many, many, many branching scenes.
Knowing a single Blu-ray disc can store 50gb of data, I'm curious about how many language options would be available in the game. Check out the confirmed list of languages below (Still waiting for official confirmation on a couple -- the Quantic Dream team couldn't name them all off the top of their heads.)
Note: A Polish language option is unconfirmed.