I've stayed at CSR quite a few times, always seems to be a walk in for breakfast. Most people hit the PM or go to the parks.
Maybe make an ADR if there is a big convention breaking up/checking out that day, or if it's a holiday time, but even then I think a walk up would be fine.
When we've had ADR's for breakfast they don't seem to have a problem seating us earlier or later when show up (read this as: oversleep!).