We've all heard the tired old story about the tourist who visits Wales and walks into a pub, only for everyone inside to immediately switch from talking English to Welsh. There have been endless variations on the theme over the years and it's both paranoid and patently ridiculous.
Why? Because we Welsh are generally a friendly bunch who are quick to welcome strangers to our beautiful country, not alienate them.
An alternative explanation, of course, is that those in the pub could have already been conversing happily in their native language before those visitors even came in. And that would certainly seem the most probable explanation in a largely Welsh-speaking area like Bangor in North Wales.