[Mr Apple]

"The San Ysidro border crossing is the busiest international border in the world."......."San Ysidro is a community that is both a small town and bustling city; a gateway from Mexico to San Diego and the United States."

[rolling_stone]

since I happen to live in or near district 8 of San Diego and have worked the US-Mexico border there, I am very aware of its city limits..I doubt you will find anyone with a birth certificate that say they were born in San Ysidro, California. Take a look at the map below which shows district 8.

Otay Mesa and Nestor are also communities in/of San Diego that border with Mexico.

Annexation[edit] San Ysidro, along with the rest of South San Diego, was annexed by the city of San Diego in 1957; an attempt by residents in 1973 to reverse the decision was unsuccessful.[7]

Imperial Beach, Ca touches "south" San Diego and is the most southwesterly city in the United States.

San Ysidro (Spanish pronunciation: [san iˈsiðɾo]) is a district of the City of San Diego, immediately north of the U.S.-Mexico border. It neighbors Otay Mesa West to the north, Otay Mesa to the east, and Nestor and the Tijuana River Valley to the west; together these communities form South San Diego, a pene-exclave of the City of San Diego,[1] thus making it possible to travel (by water) between central San Diego and South San Diego without ever leaving the city limits. Major thoroughfares include Beyer Boulevard and San Ysidro Boulevard.

district map

https://www.sandiego.gov/planning/programs/mapsua/map

https://en.wikipedia.org/wiki/San_Ysidro,_San_Diego