Portland has got to be one of the grooviest cities in the US, the place just fosters and incubates creativity. #1 Bike city in America :D
LA is kind of difficult because it's so fast and may seem overwhelming to a non-native. There are plenty of spots to avoid the city life on the outskirts of LA and if you want to get caught up in some crazy adventures - the city has plenty of spots to do that too. I have lived here for all of my life and still haven't eaten @ every vegetarian spot. Lightlife is unbeatable, and the pollution SUCKS.
Nor Cal is amazing too, I highly reccomend a trip to the Santa Cruz mountains to interact with the student body of UCSC - the protest school, they have an annual 420 event that is pretty breathtaking. Berkeley has tons of liberal celebration and San Francisco is the tech capital of the US with a concentration of most of the cutting edge minds that will evolve our species.
http://www.HappyCow.net is the #1 veg navigation tool on the web with countless reviews of eateries and shops. their iphone app VegOut is really tremendous as well.
I lived in LA for about 9 months and plan to move back there permanently soon. Anyway, while in LA, I found some great vegetarian places and it is so much more vegetarian friendly than the tri state area here on the East Coast, so I am looking forward to coming back for that reason alone! While the pollution is not great, LA county is incredibly clean....way more than here in the tri state area. By clean I mean there is rarely to no littering, etc... and it's just a beautiful place to live. Also, you can live in LA w/out a car, public transportation is everywhere, you just have to drop the pride and go (it just might be cheaper than taking your car!) trust me, I did it. There is always something to do, there is never a dull moment in LA, so you will always have a great time no matter what you decide to do.