@Mame,
I've never tried speaking Welsh. They all speak English anyway.
And not all of them speak Welsh.
All roadsigns are in both languages.
There have been some mix ups. There was a news story about a parking sign. The English was fine, but the Welsn translation said something like.
I'm sorry, nobody can answer your call, please leave a message after the
beep.
In the first Flashman book by George Mcdonald Fraser, he describes the soldiers who have returned from India as having peculiar Welsh type accents.