dude, don't sweat the trolls. Real Californians don't give a f*** where you're from.
Walnut Creek is good for lots of reasons. The schools are pretty decent, lots of good trails to run (though you'll have to drive most likely), and there is good BART access from there to Oakland (straight shot, no transfers). IMHO, though Walnut Creek has no soul, so if you're looking for a place that is not a shiny plastic yuppie wasteland, go elsewhere.
Piedmont is nice, probably more expensive, and closer to work. You can drive up into the hills and hit some trail running in redwood/joaquin miller fairly easily.
I believe Pleasanton has access to some pretty good trails, open space areas, but I'm not as familiar with that area. Also is probably pretty damn expensive and will be a bit longer of a commute.
Emeryville is close to everything, but seems like the equivalent of living at a mall to me. It just seems like condos, business high rises, and shopping. It's also probably pretty expensive, and a little further from the trails as some of your other choices.
Personally, I think Piedmont is the coolest place of all the ones you mentioned, with WC second, Pleasanton 3rd, Emeryville 4th, and Dublin 5th.
You might also consider Montclair area, which is pretty close to Piedmont. I have no idea what the rental prospects are like around there, but it's an alright place that's close to a lot of things.