Stuff that turns me onto a town:
Public spaces. They don't even have to be nice.... I mean, full of shit and trashed isn't good, but otherwise rundown parks and open spaces are nice hangouts, and sometimes more chill then better maintained parks.
Activity! Movement! Some kinda sense of people out and about, enjoying their day makes me happy. It's too easy to fall into thinking of "everyone else" as a homogenous brainwashed blob... then I get all broody and cynical... so it's nice to be somewhere were people just feel more interesting and relateable. Missoula comes to mind. Tourists are also cool because they buy stuff from me and leave their leftovers all over the place.
I'm a fucking foody, so... good food. Big organic store. I'll buy a snack and hang out inside on the wifi all day, then raid the dumpsters at night.
Some kind of wifi/shitter headquarters, with sofas and tolerant employees, if the above doesn't exist.
Better be some homebums. This is america. America has homeless people. If I'm in anything but a tiny village, and there are no homeless people, the place probably has some evil shit going on.
Trainyard. Or at least tracks. Not just because I'm into trains, but also that. Usually got good places to sleep near train tracks. Shit, even if I'm not trying to ride it's nice to at least hear trains.
Reasonable public transportation. Fuck you, Sacramento.
This is just me listing shit I like, though. A "good town" is a place that is friendly and accesible to travelers, but hasn't gotten sick of us yet. Folks can argue all day about where qualifies. I still like Portland, but say that too loud and I'll start a fucking war. You can also just try and avoid places that see a lot of travelers... basically anywhere that isnt on a mainline or near anything cool. Ain't as bad as it sounds.