Once you are through the turnstiles you can do pretty much whatever you want. We typically will arrive early for the PS and spend time taking photos up and down mainstreet and in front of the castle without anyone else cluttering up the photo.
You will often need to have your PS number to get through the turnstiles, but if you wait until they are busy checking others you can slip through (bad John, bad). Disney busses that are running early for character meals don't check for PS#'s.
Esp, for days that the park does not have early entry I like to get the meal early enough so that we are out before the park opens. That way you can wait right at the rope drop. My nephew got to open Fantasyland this way (with a wand and fanfare).