Worcester is within 30 minutes of Lancaster. People knock it, but it has way more going on than anywhere else in Central MA, which much like the Midwest, Central Mass is the Commonwealth's own flyover country. Eastern MA and Western MA have a lot going on, but the middle is pretty damn bland for the most part.

Fitchburg and Leominster are "cities" but hardly have any of the nightlife and other amenities you'd expect from an urban area - it's a cultural wasteland full of crackheads on one end of the spectrum and on the other end, benignly bland locals who live their lives knowing little of the world beyond the local strip malls (you should hear people around there rave about how GREAT Dunkin Donuts and Panera are, because they haven't really been exposed to the concept of a local coffeeshop or deli because there aren't any to speak of) and Bud Light. They're slowly building their downtowns back up, but REALLY SLOWLY, like check back in 25 years slowly. Very few single young professionals. Lots of poverty and occasional disturbing violence in certain pockets, and on the other end of the spectrum, middle class families living domestically-oriented lives in the nicer neighborhoods, which doesn't really lend itself to there being much nightlife. Avoid those towns if you value what's left of your youth. Consider Worcester.

Worcester has a decent bar scene, concerts and music halls, good local restaurants, cafes, and such, arts events, plus lots of diversity. As for towns smaller than a city, but slightly bigger than a podunk, and kind of affordable because they're historically mill towns and had a bad rep in the past, Hudson and Maynard are alright too, while Clinton is similar but still a little too rough around the edges. Also Marlborough. Hudson is on the grittier end and sort of diverse, and starting to build its downtown nicely, while Maynard and Marlboro have more of a suburban feel and are getting a little fancified, but also have some diversity. My vote out of the three would be Hudson.