I've only been to San Diego a few times as a result of either personal or business trips, but the visits have been enough to enable me to understand the attraction of the city. Granted, it's an expensive place to live, but the year-round weather is outstanding!
The United States ("US") Mint has produced commemorative pieces for two Expositions held in San Diego, California - the first was the Official Medal for the 1915-16 California-Pacific International Exposition, the second was a Half Dollar (a pair actually) for the 1935-36 version of the California-Pacific International Exposition. While both Expositions were hosted by San Diego, the stronger connection is the fact that both took place in the city's Balboa Park, with some of the same buildings being used by both Expositions.
The 1915-16 California-Pacific International Exposition was held to celebrate the opening of the Panama Canal and the many commercial opportunities it would bring to San Diego, California as the first US port city for ships traveling north in the Pacific Ocean after transiting the Canal. It was held in San Diego between January 1, 1915 and January 1, 1917.
1915 California-Pacific International Exposition Official Medal - Gilt

For more details on the 1915-16 Exposition and the Official Medal, see:
-
1915-16 California-Pacific ExpositionThe 1935-36 California-Pacific International Exposition was held in two sessions, one each in 1935 and 1946. In 1935, the Exposition was open from May 29 through November 11; in 1936, the Exposition season was February 12 through September 9. The Exposition was held to promote San Diego - and to draw businesses and new residents to the area. The Exposition was held during the time of the Great Depression; San Diego was suffering much like the rest of the country and was looking for a boost.
The commemorative Half Dollar was initially struck and distributed in 1935, but Congress subsequently authorized a second striking for 1936. Collectors commonly refer to the coins using their "San Diego" nickname.
For more about the 1935-36 "San Diego" Half Dollar, see:
-
1935-36 California-Pacific International Exposition1935 California-Pacific International Exposition Half Dollar

For other of my posts about commemorative coins and medals, including more "Quick Bits" stories, see:
Commems Collection