Aramaic, I think. And the ads say it's subtitled.
It's not often someone tries for historical accuracy in religious films; usually they're full of stereotypes or fanciful stuff. I might go and see it, it depends.
It's sad, though, that the film's getting branded as 'anti-Semitic' so readily. A Jewish leader in my city checked the movie out and said that it's fine because it's historically accurate, not deliberately biased against Romans, Jews or anyone else. It just shows what probably would have happened, based on the evidence we know.
Incidentally, it's called "The Passion of <i>the</i> Christ".