Born near Aberystwyth to Irish parants, with school friends and other peers who all had English speaking parants, it is a high probability you will grow up to be English speaking. Lets set aside the merits or otherwise of learning to speak Welsh if you live in Wales for the purpose of this discussion. Welsh language education in Dyfed in the late 1970's and early 1980's was dire unless you were already Welsh speaking. Arguments on both sides, but in the end it is a personal choice and some people have more apptitude, need and opportunity than others.
Communicating in your own language with others who 1st language is the same as your is always more efficient for the parties involved. I am in Sweden at the moment, working with people who's 1st language is not English. When I am out of the room, they all talk Swedish, when I return, it reverts back to English. No point flying in someone to solve your problems if they don't understand what you are talking about. It works well and this is an unwritten protocol which occurs across most countries for business.
I have to admit that during my 37 years living in Wales, the principle of being able to choose your language for a minority has been more important than the other parties who want or need to be part of the conversation understanding what is being said. I just zone out to it and go do something else. I have found a couple of instances this week where I have wondered into a conversation, my very gracious hosts have recognised my presence, made an apology for speaking Swedish and carried on in English. I had already zoned out and not even noticed, years of living in Wales made it an unconcious reaction.
Some may say I should learn to speak the language of my hosts. So in the last 14 years, I would have had to learn German, French, Spanish, Italian, Africance, Hindi, Norwegian, Swedish, American English (the hardest of all), Hungarian, Polish, Arabic, Czech, typically at a notice of less than 48 hours.
I am very positive about the Welsh language and I am making some progress in learning it. After spending a week in a culture where every effort is made to welcome visitors(short or long term), I do question if the cause of the Welsh language is being damaged by a minority being less accepting of the need of non Welsh speakers to be part of their conversation.