Zero tolerance applies to persons under 21 or on probation for DUI. That is the case in every county across the State.
The above information does not establish an attorney client relationship nor is it meant to provide legal advice.
I agree with the other advice. Additionally what you may have "heard" may relate to a county prosecutor's general charging and plea policy. That is, some prosecutor's offices like to announce that they never give wet reckless bargains to anyone charged with at or above a certain BAC or they claim that they never give conditional plea deals in other misdemeanor cases. Generally this is a lot rubbish and the the office will quickly change their "policies" when they routinely start losing jury trials because they are over charging cases. The point is Marin County, like all counties, is subject to California law and can only convict persons of offenses that can be proven beyond a reasonable doubt. Good luck.