Personally the Buzz Bar. Great atmosphere. good music but busy. If you fancy something a little more quite (ie, you can move) try Franco's, its a Pizza House / Bar. Tommy will no doubt be behind the bar and forcing Absenthe on unsuspecting new comers!! Great fun, great staff and of course great Pizza!!!!
try the black tiger ,it is my favorite,alex who runs it is a great bloke,i will be there new years eve ,then back last week in january then again in march.i love borovets and vodka