"I'm going for a walk."
Translation:Dw i'n mynd am dro.
Strictly, dw i'n mynd i gerdded would be 'I am going walking' or 'I am going to walk'.
(Note the mutation cerdded -> gerdded following the preposition i)
Thank you for pointing out the mutation! However, I believe that these phrases have quite a similar meaning. Come to think of it though, I don't think they're strictly synonymous. Thank you for the speedy answer (that always seems to come on the Welsh forums :) )
It can. Whenever dw i is part of a positive statement then Rydw i is always a possible alternative. If you come across a sentence like this again it would be best for you to report it.
"Cerdded" is "To walk", whereas "mynd am dro" is literally something like "To go on a turn" which we use to mean "To go for a walk.