Vermont tried this a few years ago, they had to cancel it since in the end it wasn't financially feasible [1]. CA is already dealing with severe budget issues [2][3], so while it sounds nice in theory I'm hesitant to believe the finances actually work out.
[1] http://www.politico.com/story/2014/12/single-payer-vermont-1...
[2] http://www.latimes.com/projects/la-me-pension-crisis-davis-d...
[3] http://www.cnbc.com/2016/05/26/californias-revenue-picture-d...