Two cities I have lived in and really liked were Chattanooga Tennessee and Portland Oregon. Chattanooga is small maybe 175,000 people or so. It right next to a mountain. There is a big college, lots of bars, parks, mountain sports and rent is about cheap as you will find in a city in this country. If you live right in the city you can bike, walk, or ride the bus without worrying about a car. There is also an awesome tight knit punk rock scene there. Toothless Tom has been having basement shows in his house a couple of times a week for years.
Portland is quite a bit bigger and a little more expensive but definitely cheaper to live in than Seattle or San Francisco. You can ride a bike, train, bus everywhere there with ease. The people there are fascinating and march to there own beat. You can find something for you whether its activism, hanging yourself from hooks, every genre of music and all kinds of wacky things. And its 2 hours to the Pacific and an hour or 2 to Mt. Hood. You can hike all over the woods out there, snowboard, skateboard the best concrete parks in the country or surf the coast. Oh yeah weed is pretty much legal in Portland.
Both cities are good places to nerd out drink coffee and read.