The nasal accent is common to a large part of CA from LA county and inland up through the Big Valley. It's actually a carryover from the Oklahomans, Kansans and Missourians who settled a lot of that part of the state but there is a difference between the Coastal, Inland Empire and Big Valley versions. There's a reason Bakersfield is known as West Tulsa. :)

The Bay Area has another accent, with palatalized dental stops you don't hear anywhere else in the US, "tyoo" for "two" and "dyoo" for "do". San Diego has a rhythm that is different from LA, it all sounds like people are thinking in Spanish; it's also faster than LA. Sacramento has an almost East Coast Big City flatness to the vowels, probably from German and Irish immigrants a hundred and fifty years ago. The northern parts of CA sound more like Oregon, Idaho or Wyoming. All these effects are pretty subtle.

The radio/TV age has had an odd effect, leveling some accents but not others and in fact, there has been a spread in the US of a new vowel shift around the Great Lakes that only started after television. It ain't that simple, apparently.

Hugs,
Erin