If you don't use pullups on those pins they'll be like the Grand Old Duke of York...they won't know whether they're up or down 
I use interrupts whenever I need them.
For instance (if I could get the IRQ line to respond 
) I would play through 36 frames of data, then have the interrupt fire, then change the data and restart the movie with new frames.
I'm doing this at the moment but I have no control over when the change happens - if I used interrupts I would be in charge... ]