This weekend in the arts: Magos Herrera and Brooklyn Rider at the La Jolla Music Society; City Ballet's "Romeo and Juliet"; Julia Margaret Cameron at MOPA; Bert Frings and Bas Louter at Oolong Gallery; Bach Collegium San Diego's "Scorchers"; Moxie Theatre's "The Chronicles of Kalki"; and pompom pride flags and free admission at OMA.