Cleaning on a fixed schedule is mostly a matter of convenience for the boat owner. If you'd rather call your diver when you want service, that's fine too. Again, the Port is not requiring a set schedule for cleaning.

Regarding how foul your hull is becoming after 3 months in San Diego Bay; one man's underwater jungle is another man's acceptably clean bottom. The fact that your diver is afraid that the plume of wiped-off growth from your boat might be mistaken for anti fouling paint tells me there's more than just a light slime coming off. And I know you don't have some magic paint that works better than everybody ele's down there.