I think they screwed up a little bit, nothing major, but they could have done some things better.
I went with my family last Sunday, and like the article says, pretty much everything was in Welsh only. It's great that it's a Welsh festival and promoting the Welsh language, but if you don't speak Welsh there's no provision for you. We spoke to a few people who said that they were struggling because of it. Every other non English language event I've been to around Europe has had at least some alternative signage.
They mentioned maps in the article, but we found out by chance that there were maps available because we saw someone with one while we were halfway around. There was nothing to say that you could buy one anywhere at the gate we entered through. We ended up going the long way around the park and missing a lot of the stalls because we ran out of time.
Like I say, nothing major, but there are some things that could be improved :)