Rules are explained once you reach the top of the building and before riding King Khajuna, but there is always some people that may refuse to follow or just feel scary enough to forget them in middle of the drop!
PortAventura started their "White Night" event for summer, some days the park will close at 4 am, with extra time to enjoy rides, more shows and additional fun with special street acts (live orchestra music, flamenco, foam party, dj's and so on ...).
Here is a little video I recorded of the first White Night in may.
http://www.youtube.com/watch?v=av7b5qtNUVk
White Night's for 2013 are scheduled with blue background in this calendar: