Some states, Pennsylvania among them, allow for rent to be escrowed when the rental is in violation of that state's housing code. Your situation interfere with your right to "quiet enjoyment" under the lease/PA law, but I doubt it's a code violation. So, short of reaching some agreement with your landlord, your only real option is to break the lease. I did that myself in 2002. My situation was arguably worse than yours in that it involved some crackheads across the hall from me who posed a physical danger to me (they were eventually evicted when one of them stabbed someone in the apartment). I vacated and was initially with the thought that I'd just wait until they sued me. Instead, we reached an agreement whereby I paid part of the rent due for the remainder if the lease and washed my hands of it. I still sort of wish I'd let them come after me. I would have delighted in detailing the horrors of my neighbors and how little management did in response. I kept a record of everything.

I'm not necessarily recommending that you break the lease as there's obviously a big downside financially if you get sued. I had the money at the time and I'm an attorney so I felt comfortable with the risk. I hope for your sake that your landlord can accommodate you. Have you tried talking to these neighbors yourself or are they too scary to approach? What, if anything, does your lease say about dispute resolution?