Bethesda? Good luck with that one. Used to live near there, and worked with a resident of the town for a good few years. His hobbies were mainly shooting crows from his bedroom window, and fighting every Friday night outside the pub. He genuinely thought he was a Wookie.
Bangor or Llandudno for a night out – although you may find a cheap coach trip to Rhyl and the “club scene” there. Llanberis OK for a bit of food.
Having said that, as above really; I’m from the Midlands, lived in North Wales for five years, no trouble anywhere in any pub. Go with an open, happy disposition, spend some cash, and you’ll have a great night out anywhere really. The only fighting I ever saw was between brothers or long running feuds with neighbours who were always mysteriously from up / down / over the valley.