By Heidi Gantwerk Heidi Gantwerk SAN DIEGO — One week ago today, I stood in a plaza in downtown Mexico City with 28 fellow travelers on our Federation mission taking in the view of two of the oldest synagogues in Mexico: Mount Sinai, built in 1918 to serve Jewish immigrants arriving from the Middle East, particularly Syria, and Justo Sierra, founded in 1941 to serve the community of refugees from eastern Europe who made their way to Mexico around WWII. After spending over 30 years in San Diego and getting to know so many members of our dynamic Mexican Jewish community, I have long wanted to ta…