We've done both in the past - used the bus or rented a car - and we're renting a car again this year when we go in December. In pricing it out it's less than $200. Which may seem like a lot, but I know I will worry constantly about getting to ADRs etc on time. I like being able to come and go as I please - and since we've planned some "off time" during our stay we'll be able to drive off site if wanted. As for clothes and what to wear from a PP - I'm going with layers this time around. When we went in Dec two years ago - it was nice during the days (I wore jean and a fleece all week) and very cold at night. Some days were warmer than others. I'm a new englander and usually wear flip flops until it snows so my cold tolerance is very high. So pack a little of everything!