What are the most socially liberal towns/counties in the South?

[Smash255]

I think Arlington is pretty liberal, but not really as its not really much of a college town.

I would say Arlington is fairly liberal, it is a Democratic stronghold & unlike some of the other cities listed the surrounding areas of Arlington aren't Conservative either  (Fairfax use to be, but not anymore)

[Smash255]

...excluding Florida...

Perhaps:

Chapel Hill, NC
Carrboro, NC
Durham, NC
Asheville, NC
Atlanta, GA
DeKalb County, GA
Austin, TX
Arlington, VA
Nashville, TN

Austin's a state capital.  State capitals are always more "liberal" than the state, in general.  Not unlike Boston or Sacramento or Nashville.  (yes, I know there are counterexamples:  Tallahassee comes to mind.)  State capitals have several important features in common:  1.  because the workforce depends heavily on government/education and socialized resources, they tend to be big government types.  2.  also because of this effect, state capitals tend to weather economic downturns better than the rest of the state.  3.  because capitals bring together people from diverse and far-away places (both ideologically and geographically), people who live in state capital cities get used to strangers and strange ideas quickly.  And a state capital like Sacramento or Austin would have that phenomenon more than most, since they are the capitals of the most- and second most-populous states, respectively.  They are also, respectively, the state capitals of the 3rd-largest and 2nd-largest states geographically.

For the South, I believe your argument will generally hold true.  The example of Sacramento, though, is problematic because the Sacramento metro area is somewhat more conservative than the Los Angeles metro area and a lot more conservative than the Bay Area, making it somewhat more conservative than the state as a whole... in states with mega metropolitan areas that skew the state's overall ideology (California, New York, Illinois), the state capitol is likely to be more conservative than the state as a whole, probably for the reason that you mentioned--that the capitol brings in people from all over the state.

Well in New York's case while Albany is more conservative than NYC metro, its slightly more liberal than the state as a whole.  Went to Kerry by 23, the state went to Kerry by 18, Albany went to gore by 27, the state 25, in 96 the state went to CLinton by 29, Albany Clinton by 33