People in Santa Barbara County vote conservative when the issue is their money, and keeping their money. Monterey County less so, but I'll try to give a go at explaining my initial assessment. Much of this proposal has to do with people keeping more of their hard earned money.
The proposal was originally written after the recall election. Santa Barbara County easily hit the conservative note on recalling Grey Davis when the main issue was one of personal finance and motor vehicle fees. Monterey County was not as enthusiastic for the recall effort in the more heavily populated northern parts of the county, but was very supportive in the southern rural parts that comprise most of the county. I was told that a final well prepared proposal can bring the rural parts of Monterey County into the new larger state.
There are national statistics published showing which states contribute and receive money at the federal level.
For example, most of the south (red states) get more than they send to the feds.
I have no idea how this would work out, for the counties in California. I expect some large counties like San Bernardino receive more than they send to Sacremento.
In any event, I don’t expect a proposal like this will get far, at all.
I live in Orange County (red) where I can drive a few miles one way into a city very full of illegal immigrants, and a few miles down the coast to Newport and Laguna Beach, with very high incomes.