I think that's smart -- taking a year off is not a bad worst-case scenario. It's amazingly nice not to have homework for awhile, and to figure out exactly where you want to be.
I decided to stay on the full-time-only waitlist, just to avoid any weirdness with part-time. AU makes it sound like it's not a big deal to switch from part-time to full-time after the first year, but who knows how complicated it is if you were to try to transfer to another school, do a joint degree, etc. -- I haven't researched part-time at all.
Oh and fyi -- it says on the Wait List Requirement Form that if offered a spot, you have to let them know at the time of the offer whether you will be accepting. Since they do it by phone, I may be screening all 202 area code calls for the next few months just to give myself more than 15 seconds to make up my mind for good. That $700 seat deposit is nuts.
Anyway good luck to you whatever you do.