I made last-minute plans to go to WDW during Presidents Week this past Feb. 17-23, after a previously-planned trip to Haiti had to be cancelled the night before I was to fly to Orlando. My biggest problem was finding onsite lodging, so I ended up staying at 5 different hotels the 7 nights I was there! Fortunately, it was a solo trip.
Yes, the parks were crowded (Epcot not as much), but I was still able to get fastpasses. The crowds were heaviest Sunday and Monday, then were considerably lower as the week went on.
As others have said - go and enjoy what you can. At least with an AP, you don't feel like you are wasting a day of admission if you don't spend much time at the parks.