A Time to Cast Away Stones by Elise Frances Miller

Janet Magill’s brother has been shipped off to Vietnam, and Aaron Becker, her childhood sweetheart, might well be next. When Janet’s parents banish her from the Berkeley protests to what they expect will be a safe, idyllic springtime in Paris, she runs headlong into the 1968 May Revolution and falls in love with a secretive Czech dissident. Far from the City of Light, Aaron makes plans to evade the draft and join her, but loses contact as her "safe" year abroad turns into a dangerous coming of age.