Hi Heather! I think it is awesome that you are planning to run the Princess half in 2013! The Princess was my very first half marathon ever and holds a special place in my heart. Being able to run through the Disney property is an amazing experience, especially if you are already a Disney lover!
The race dates for the 2013 Princess have not been released yet, but it will most likely be either February 24 or March 3. (obviously, this is subject to change, but it has always been one of those two weekends in the past).
As for walking, ABSOLUTELY, it is not only acceptable, but prevalent! 45% of the runners at runDisney events are running a race for the first time. Additionally, runDisney's official trainer,
Jeff Galloway, is an Olympic athlete who not only recommends using a run/walk/run interval method for running, but also does it himself. I have tried to run half marathons without taking walk breaks and actually end up with a slower overall time than when I use a run/walk/run interval. Definitely check out
Jeff Galloway's training website. When you sign up for a runDisney race, you will actually receive a free training program from Jeff Galloway that is customized for that particular race. And lastly, there are a large number of participants in the runDisney half marathons that choose to walk the entire time. Disney races are all about moving your body, reaching personal goals, and having fun. Crossing the finish line should be your ultimate goal, no matter how you get there! Please feel free to send me any questions you may have about races or trip planning as you prepare for your race! Good luck!