Hi West Coast;
I see that the folks with an earlier get home time got to you first <G>. What you have already been told. The majority of how any airfield in the US is run is designated by the airport management. From opening and closing times ( not the tower or approach ) to patterns and other such wonderful things. We just have to try to comply with the restrictions. SNA is a GREAT example of trying to make stuff work due to airport management restrictions.
regards
Scott