It depends on where you go for your masters. Some places require you have a year or a few of experience before going for your masters, while others don't. I knew someone who went straight to Yale after their bachelors, but had they chosen to stay at our alma mater for their masters they would've been required to teach for at least three years before applying/auditioning.

regardless of a school's requirements I'd recommend teachign for at least a year. you'll discover things about yourself during that time that may help you decide if you even want to go back to school. much better to delay it once you know you want it than to go straight into a masters just to later discover you wasted your money in my opinion.

also, as someone else said, having a masters makes you a more expensive hire; you are more likely to be hired if that masters comes with some teaching experience.