If I speak Welsh, will I be able to understand Patagonian Welsh ? And for native Welsh speakers, how much of Irish can you understand because of your native tongue ?
If you speak Welsh you will understand people from Patagonia entirely, at least from my very limited experience of Patagonian Welsh. As for Irish we understand basically none. Irish is a Goidelic language whereas Welsh is Brythonic. They both came from Proto-celtic but the vocabularies are almost entirely different and the only thing linking them is the grammar. We can understand a little Cornish and Breton though.