On May 24, 2012, Their Serene Highness Prince Albert II and Princess Charlene of Monaco attended the “… second practice session at the Monaco F1 Grand Prix…” Whilst there they mingled with attendees as well as the security staff.
And, finally, if you were wondering why Princess Charlene did not attend the charity gala event, Nights in Monaco, apparently the event was a “gentleman’s evening” only according to the Palais Princier de Monaco. Click here for more information. (scroll down)
Sources: Daylife and People via the Palais Princier de Monaco