Not just hella
Though “valley girl” talk is a well-known dialect feature of (some parts of) California, I find it’s not extremely common around where I live, nor does it seem to be for the rest of the East Bay, even among my (current and past) friends who’ve grown up in northern California. But once in a while, I’ll hear it around campus and in coffee shops, and I’m absolutely fascinated by it, because it seems to be legitimately spreading. (It could be that I just don’t hang out with the appropriately vocalically-vulnerable people.)
Of course, you don’t have to be from the valley, or even be a girl (or a woman), to show the characteristic tendencies. I highly recommend the sound files on Penny Eckert’s site, which shows, I believe, mostly schoolchildren from the southern part of the San Francisco peninsula. I personally exhibit (almost) none of the uniquely Californian vowel shift. (The only possibility is a palatalized /n/ before /i/, which might be the result of /i/-heightening (though not in the environments noted on Eckert’s site.) And this may be a good thing, since according to some, when I try to imitate the changes, I sound like I’m “from the Castro.” Whatever that might mean…
(And yes, I’ve certainly heard men (who I guessed were not from anywhere in San Francisco) in the 18-35 range with some of the vowel changes. It totally boggles my head to hear it, though.)
And relatedly, I know a couple of young kids (both under 6), one of whom seems to consistently have /E/ for /I/ (pronouncing the name Nick as /nEk/). The other one, who is older, seems to most people to have the standard English that you get out here in California, but the other day I noticed her announcing the age of one of her friends as /sEks/ - that is, 6. It may be to early to see if this actually a result of the /I/-to-/E/ change noted on Eckert’s site, but it would be pretty interesting if it were.
(for some more samples and text on Californian speech, there’s the Do You Speak American coverage of California, which is passing good.)