Fisherton Street is lined with pubs & the Chicargo Rock cafe & The Kings Arms is here as well. On Saturday night's about 8pm it can be a bit noisy, & late at night after the pub's have closed it can be a bit rough. You can also see lines of cab's waiting to pick the drunk up. Police cars patrol up & down & sometimes there's a fight outside the pubs after closing time.
Greencroft & The Town path are best avoided at night as well. The lighting isn't good along the Town path, so if you go that way, make sure you are acompanied by a friend; not a wierdo.
Be careful going to pubs outside the well traveled city center and "touristy area." Hiking, I stopped at a pub on the outskirts of town, after dark, and was told that "yanks aren't welcome here." by a group of patrons. I almost got into a fight. Fortunately, I decided to leave quickly and keep moving till I got to a more populous area.