Mexico City is 1 hour ahead of San Diego
Best overlap: 8:00 AM to 5:00 PM in San Diego is 9:00 AM to 6:00 PM in Mexico City.
The overlap falls at 8:00 AM to 5:00 PM in San Diego, or 9:00 AM to 6:00 PM if you're in Mexico City. Mexico City is 1 hour ahead of San Diego, and with 9 hours of overlap you can even run back-to-back calls without stepping outside business hours. Just remember San Diego changes its clocks for daylight saving and Mexico City doesn't, so confirm the overlap whenever the seasons turn.