Depends what kind of job you are seeking. You should have a copy of the PC1203.4 "Order Granting Dismissal" issued by the court when your case was "expunged." By the way, it wasn't "expunged" as there's no such thing in CA. Read the court order very carefully and let that guide your answer. Best of luck, you are on confusing ground here.
San Diego Criminal Defense Attorney--19 years experience. Law Offices of Jay S. Finnecy
Just to elaborate on my colleague's answer, if it is a private employer you can say no. If you apply for a government job or for a license from a state agency (to be a lawyer, accountant, real estate salesperson) you must disclose it. There are other situations where it must be disclosed. As my colleague said read the order.
When you say "they," are you referring to a prospective employer? If so, the answer to your question depends on who the prospective employer is (assuming the conviction has been expunged). You should speak with a local attorney.
I agree with my colleagues answers. It comes down to who the employer is.
Attorney answers to questions are for general purposes only and do not establish an attorney-client relationship.
California does not have a true "expungement" statute. What we do have is a dismissal under Penal Code 1203.4. If granted, it doesn't wipe the case off your record, but it adds a notation that the case was dismissed. That allows you to tell most employers that you have not been convicted of the crime, but it remains on your record and still counts as a prior conviction.
Read the code section to see the exceptions to nondisclosure.
The above answer is for general information only and is based on the information you posted. Every case is fact dependent, so to get a thorough analysis of your situation, you will need to consult face to face with an attorney licensed to practice in the jurisdiction where the incident took place. Do not conclusively rely on any information posted online when deciding what to do about your case.