My brother sent me this photo the other day and at once, the mind starts working as to what was happening this day for so many cars being parked here. Must have been a big event in Balboa and could have been a sporting event at the ball field or swimming pool.  I took the photo and zoomed in on the white jeep type truck and the logo on the door looks like that of the Red, White and Blue Troop swimming team and  performers.   See the link below.   

https://czimages.com/CZMemories/Photos/photoof952.htm

 https://czimages.com/CZMemories/Photos/photoof954.htm  Could have been a visiting famous person like Admiral Byrd or Lindbergh who both visited the RWB troop at Balboa Pool.

Super nice photo and I will bet the event was what I mentioned above.  I wish I had an exact date to run a dating search.

Thank you for sending the photo Barry.