According to CA PC 1203.4, if the charge was properly dismissed under a section of that statute that allowed for it, the conviction is not a conviction any longer and is considered a dismissal. This means that you haven't been convicted. The conviction was for all practical purposes, overturned, so an answer of "no" would be truthful under this scenario.
Your question is slightly confusing. It states "as to count 1.." You didn't mention the dispositions of any other counts of the charging instrument. If additional counts that you were convicted of weren't dismissed, then you have been convicted of something..
Also, the answer required here depends upon the job your seeking. If you are seeking a public service job instead of one in the private sector, disclosure with an explanation is your best bet. Cali law also suggests that disclosing is required if not a private sector job.
Bottom line- if you think they might find it, its probably better to err on the side of disclosing. That way, you aren't hiding anything and they will confirm or deny your explanation when they do find it, or disregard it altogether when they don't find any record of a conviction.
The answers here are not meant to replace the advice of a licensed attorney. My practice is in the San Antonio, Texas area and I am available to provide more information upon request by any potential clients.
Technically you received probation and successfully completed that probation hence the language you described about the case being dismissed. In Texas, that language would not entitle you to an expunction of the charge so the matter would remain on your criminal history. Since the application is worded "ever been convicted or received deferred adjudication" I am afraid you must answer yes, otherwise the employer will discover the criminal record and probably consider you dishonest.