Portland, OR - meets all your criteria except maybe cost of living. Though that really depends on your standards. But the public transit is top notch, it is also a great place if you like to commute by bicycle. Check it out...
Portland has decent public transit, its cheap to live there, and you can find decent jobs. Although you may not find a wide variety of jobs that aren't corporate. On that note I will say there are a couple startup incubators in town but those jobs fill up quick.
I ended up moving to San Francisco. Great city. Expensive, but fantastic public transit and tons of jobs.
Here are my list of cities in no real order: San Francisco, CA Portland, OR Seattle, WA Boston, MA New York City, NY
Check them out. If you like a few, spend at least a week exploring and getting to know the city a little bit. Also try and go during the worst weather period so you really know you can live there.
Portland is way to proud of a middling effort at best.
The city has no immigrants (I make a habit of counting the number of non white people when I am there... High score was 15.)
Also the tech scene is middling at best, for example if you go to the 'tech' coffee shop downtown, everyone there is updating their myspace pages and playing counterstrike.
The last big thing to come out of Portland was upcoming. (Although Aboutus just did a round of funding. (Wiki company)). HP (Corvalis) and Intel have huge offices nearby...
In short if you want to have a nice life and be a hipster for your twenties-thirties, move to portland. If you want to try and hit it out of the park, pick someplace else.