Well... Seattle is on the Left Coast along with California, is that "centered around" California?
@moonliner occasionally performs with Golden Road (yes, playing that awesome Alemicized Starfire), I've seen them at Nectar Lounge a few times.
There are other bands/artists around the Puget Sound area that are at least Grateful Dead cover bands (not really "tribute"). And I have to admit that even though I'm not playing in overtly Grateful Dead bands, I take some inspiration from Phil in a lot of what I play.