I'll take issue with a couple of posters who said "have a goal." My advice would be stay open, be flexible. The longer you stay in a place, the more layers of the place (and of yourself) will be revealed.

Re: your return, you already know the answer. If staying on a straight and narrow traditional career path is your objective, you wouldn't be considering this trip. The trip will change you and what you're looking for. I traveled when I was 27/28. The gap in my resume - and the explanation that went along with it - were the best possible screening mechanism for prospective employers. Some of them couldn't relate; those weren't the folks I wanted to work for. Others loved the idea, and had taken similar journeys themeselves; those were the places I wanted to be.

There was never a millisecond during which I regretted taking the year off. Good luck!