Testing Locations » California » San Diego CA » Quest Diagnostics – San Diego First – Employer Drug Testing Not Offered Quest Diagnostics – San Diego First – Employer Drug Testing Not Offered Quest Diagnostics – San Diego First – Employer Drug Testing Not Offered1855 First AvenueSte 200-BSan Diego, CA 92101-2685 United States Located on the corner of First Ave and Fir St. Inside Physician Dr Houghton’s office.