You are hitting the heart of Brazilian Tour Group season. A lot has changed since 2004, Brazilians are the #1 visiting nation overtaking England and Dec till Feb is their summer vacation.
Jan used to be off peak time but that is a thing of the past with the Brazilian Tour Groups overrunning disneyworld and universal. Just google Brazilan Tour Group Disney and be prepared.
The key is to find out which park the Brazilian Tour Group will be at and go to the other park. I was at Universal last February and had the park hopper. Universal was somewhat crowded but then when I went over to islands of adventures it was packed because the Brazilan Tour Groups were all at that park.
The best times to go now are in October and maybe may. Dec-feb and July are times you do not want to go because it coincides with their summer and winter vacations.
And in general weekends are worse because of more locals and americans flying down just for the weekend.
I would try to get as much done on Friday as possible cause wait times will be longer on weekends.
just be prepared for the parks to be very crowded compared to 2004.