Hi Pam, The California Death Index reports deaths by County only. You don't know from this info if he died in San Diego city or county. San Diego county is HUGE with many towns and cities.
You can order a copy of his death certificate which will be as accurate as the Informant was. Then if he died away from where he lived (in hospital, on vacation, etc.), you might end up searching where he didn't live. Information about how to order a copy of his death certificate can be found at San Diego Assessor/Recorder/County Clerk, arcc.co.san-diego.ca.us/services/birthdeath_certificates.aspx .
Before you pursue that option, here's contact info for volunteer in San Diego City. Go to freepages.genealogy.rootsweb.ancestry.com/~obitl/volca.html Scroll down to San Diego and choose ONE of the options there.
You can contact the San Diego Library, sdcl.org Hoover over Community Services Click on Libraries Click on AskALibrarian on right-hand side of screen