If you take the boat, you get scanned at the boat dock (at least RPR had the walk through metal detector while SF had hand held one...we walked from SF because the boats were not running at the time due to lightning, we had a walk through one at the end of the path....I saw the HRH walking path one when we went by the hotel guest HHN entrance, if you walk, you get scanned at the end of the walkway.
Do not know about now, but the rules use to be if the posted wait time was over 30 minutes, you got a return time, if it was posted under 30, you would get to go in the Express line right then.