If all you care about is transportation, you can get a very cheap small motorcycle (or dare I say, even a scooter?). I believe many 250 cc engines can get upwards of 70 or 80 mpg. No motorcycle insurance required in Washington but if you want it, it should be cheap because motorcycle insurance climbs sharply with engine size.
Even if you want something with more style or power, it'll save you on gas. I've owned 600 cc and 1100 cc bikes that have both gotten above 40 mpg.