Are you a third-year? I'm assuming so. I'd recommend studying during the year if you're not taking an overly burdensome schedule and taking it in May or June. Just FYI, the last date you can take the exam to have your scores available on June 1 is May 1. I would take it ASAP to ensure that you're not sitting on your hands waiting for your scores to arrive.
That said, don't take it before you've put in some serious studying.