I asked of a number of friends with varying degrees of fluency and received a number of different suggestions:
“The traveller has lots of stories - but there is inference that the traveller can lie with authority especially if he is in the company of people who don't travel - he can spin yarns”
“The conclusion is that meaning is obvious but translation difficult if not impossible.
“It means “ The traveller is a storyteller” or “The person who travels has stories to tell”
“Bíonn siúleach scéalach = You learn on foot... informed on foot... I know there is an english cliché but it escapes me ... basically, the best information is from the source or on the ground ... on foot.
Resorting to the web has thrown up some other alternatives
“One interpretation is a variation of the American proverb, "Travel broadens the mind," and the English axiom, "He that travels much knows much." Such a traveller returns with a great store of sagas about his peripatetic exploits. On the other hand, there is another interpretation explicit in the English language proverb that says, "A traveller can lie with authority."”
'Bíonn siúlach scéalach' means 'travellers have tales to tell,' ie 'travel broadens the mind'
Travellers Have Tales To Tell
“Bíonn siúlach scéalach.
She who has travelled has tales to tell.
travellers have tales to tell
Bíonn Siúlach Scéalach - A Traveller is a Storyteller
If the objective was to promote discussion and comment, the installation has succeeded