The short answer.
No, tint is not allowed in California on the front windshield or front side windows.
Tint is allowed on any windows located behind the driver, as long as the vehicle is equipped with a right side mirror, like most are. The tint can be as light or as dark as you want.
There are some vehicles that only have the minimum of a left side mirror and a rear view mirror. Those vehicles cannot legally have tinted windows. My first car was like this and had no right side mirror. I tinted the rear windows, not aware of that requirement. I had the car for 6 years and was never stopped for the window tint.
Here is a photo from the internet.
As you can see, their lightest example of 80% is too dark to be California compliant. 88% film is for UV protection, and really is a clear colorless film. It has to transmit 70% of light when installed, which includes built in factory glass "tint". This is what a standard window is on a normal car without tint applied + the 88% film = at least 70% light transmission. Applying 70% tint film is not legal. Also, to be legal, one must have a doctor's note with them at all times, or a certificate from the installer with them, at all times, to provide to an officer along with the 88% material installed. The certificate would certify that the material installed was 88% UV blocking California compliant material. I would not call this material tint, because it is clear and colorless. Basically, no one should be able to notice any tint, or darkness to the windows. If I can see that the window is tinted, and it is a windshield or front side window, then it is not legal in California. This isn't just my opinion or interpretation of the law. I've heard this from a judge in traffic court as well. When the law changed to allow the film with a manufacturer letter instead of only a doctor note a few years ago, many news stories claimed that California now allowed front tinted windows, and this is simply not the case. So the confusion is understandable.