It would be extremely discourteous, not to mention bad for business, for any shop in Wales, or elsewhere, to ignore the local language.
I listened to a Los Angeles Theatre Works (LATW.org) version of Under Milk Wood on Saturday evening. Not as good as the original BBC version, but not bad - although some Welsh pronunciations were a bit off, and somehow Coronation Street is introduced as the main street of Llareggub. I doubt very much if there is any such street anywhere in Wales. As Wales is a Principality, the Coronation is not very relevant to the country. Charles is not King of Wales.
Credendi non mutant facta