Yes. Tape a cop. In California you can record any conversation to which you are a party, legally.
And no, dont tell him about your plans. ASK HIM HIS GUIDELINES FOR HIS DEPUTIES! This does not include discussing the 25 plants in the trunk of your car, or the 10 pounds of heroine your cousin is packing through customs in his anus.
Questions are not illegal. If you hold a medical cannabis card in California you have a RIGHT TO CULTIVATE and his guidelines will be the place to start. Just like asking about his rules for concealed carry permits, the sheriff makes the rules for the county's deputies, and is usually more approachable, sensible, and available for questions than the nearest big city Police Chief or your mayor.
If you start by asking, you will get either a negative response such as "we dont cotton to no dopeheads round here", a specific set of rules he has implemented for his county, or a "no controlling legal authority" response. If you get his opinion in writing you have a much better position in court, if he wont give his opinion in writing, then a tape of him sayin for example "you can grow whatever you want as long as you stay within SB 420" then you have a strong position if ever busted (if you stay within his guidelines of course)