There was a local event in 2002, in certain parts of San Diego County, where snowlike hail fell- no snow.
I presume you mean snow that actually makes it to the ground. This is a very rare phenomenon in inland San Diego County, which can have very chilly, below-0 nights in winter- I have lived here 34 years, and recorded snow has fallen in areas like El Cajon or Lakeside perhaps once a decade- never more than a dusting, and it disappears as soon as the sun comes out. There has been no snow in the coastal or desert areas during this timeframe.
I could find no record of snow either for San Diego (on the coast) or El Centro) in the desert. I did find that an inch of snow fell in Phoenix in 1933 and 1937, per wrh.noaa.gov/psr/general/trivia [no longer exists]; it's possible but unlikely that this extended as far as El Centro, which is about 100 miles away. NOAA records that I could find list only "precipitation" for an area; they don't break it down by whether it was rain or snow,
Infrequent measurable amounts of hail occur in San Diego, but snow is practically unknown at the Weather Service Office location. In each occurrence of snowfall only a trace was recorded officially, but in some locations amounts up to or slightly exceeding a half-inch fell, and remained on the ground for an hour or more.
wrh.noaa.gov/sgx/climate/san-san.htm [no longer exists] does state,
The Weather Service office is located at Lindbergh Filed, which is on the coast.
So the answer seems to be- yes for snowfall in San Diego, probably not for El Centro.
