I agree about personal names (it would be rather absurd to insist on turning Ieuan ap Dafydd into John Davies and vice versa) -- but the fact is that where two place names exist for one locality (say: Abertawe and Swansea) they ARE each used in their respective languages (Wyt ti'n byw yn Abertawe? / Do you live in Swansea?), so it is important to know, and to be able to use, the Welsh forms.
Yes, all directional signs etc. in Wales must be bilingual by law. See these examples:
That doesn't alter the fact that -- alas -- most people in Wales don't speak Welsh and, outside those living in the immediate area, would be unlikely to be able to help if you asked for directions to "Abergwaun" (whereas "Fishguard", although the town is only a small one, is fairly well known, even in most parts of England, as one end of an important car-ferry route linking southwest Wales to southeast Ireland).
It's interesting that on the second sign (above) the last lines (though they refer to the same event) are not quite an exact translation of each other:
Glaniad y Ffrancod ( = Landing of the French) 1797 The last invasion of Britain
Exactly Dizzily Enchanted. In Ireland now official place names in Gaeltachtaí (Irish-speaking areas) must be in Irish only. You may have heard of the controversy when the tradespeople of An Daingean lobbied to keep Dingle on signposts, saying Tourists wouldn’t have a clue where An Daingean was. Being a native speaker I do resent how the English colonists made us change our place names and personal names when the invaded Ireland. But I know that’s not relevant in Wales as you are happy to be part of the UK. But at the end of the day Duolingo is for learning languages not geography. I’m not interesting where Fishguard is I want to learn Welsh grammar, and vocabulary that is relevant to everybody whether they live in Wales, Ireland, or America etc.