Whether it's easy or not totally depends on your credentials, your flexibility in terms of geography, and what kind of school assistance you are going to have. If you are competitive for advanced and categorical programs, one would think that there will be a prelim somewhere that will take you. However it is not unusual for there to be few options in a particular geographic area. So are you willing to move to work at some suburban hospital far from your med school or advanced program for a year? And does your med school help out with the scramble? Will someone pick up the phone on your behalf and start calling their contacts at programs which still have spots?
I know a few folks who miscalculated and had to find a prelim spot despite matching very well in terms of advanced programs. I also know some people who didn't even apply to prelims and just applied nationwide in the scramble for dead end surgery prelims (didn't waste their time with IM). Both groups ended up fine, but with a lot more anxiety than necessary, thinking they would have to give up their advanced slot for lack of a prelim (which happens to a few people on SDN every year -- they lose the game of musical chairs).
So I probably wouldn't move up the categoricals on your list if advanced are the goal. But just get your mind ready for the fact that you may be moving to nowhere to be the only non-IMG at some malignant prelim for a year if you end up in the scramble. Which is why folks should really try to steer their way away from the scramble to the extent possible.
