Chelle is absolutely right. I had a pretty graphic demonstration of that, too. I had a raised bed that I planted a few daylilies in, and only had enough mulch to cover half the bed. The following spring....Yow! The mulched side had a few, easily controlled weeds poking up. The other side was a mess! And that was with a much thinner layer of mulch than Chelle is recommending. I'm also fighting the same sort of problem in my rose bed. I'm slowly getting the larger weeds out and mulch laid down and the mulch is making a huge difference in new weed growth.
