Morgan is the same way on the beach.  she is good most of the time we are there and then she sees people walking along the beach and its good bye mommy, hello new people!   she just loves people and other dogs so much.   I tried a few times with her letting her off leash and seeing what she would do and its hopeless.   she'll go home with anyone 

  now she stays on a retractable leash for her own safety