The powers that be at NASA cringe at the thought of the eyes of mere commoners like us falling on the shuttle. The shuttle is always moved out to the pad at night (after visiting hours for us serfs are over), lest we actually get to see it out in the open. As soon as the shuttle has reached the pad, the service structure is closed to prevent us from seeing it, as well as to protect it from the salt air that close to the Atlantic.

Yes I'm sarcastic, but I long for the good old days when NASA was a lot more friendly to the public.

The closest you can actually get to the shuttle is to take the NASA UP Close Tour available through the KSC Website. This tour cost extra on top of the regular admission, but they do take you onto the causeway where you can see the pads on the Air Force side far better than you can from the KSC side. They also drive you out to the camera stand between Pads 39A and 39B where you can get a good look at the external tank and the boosters. The tour also stops near the Vehicle Assembly Building, and takes you out to the landing strip where you can look at it, but not get out of the bus.. You can do that tour up until a few days before the launch goes up.