I don't really 'celebrate' it as such, more just recognise it.
I wear a daff on my coat, and have some in the house. The little'un has taken a bunch for her teacher.
When I was a kid, I remember my Dad going out drinking when it was St Davids Day, with his Welsh mates... sorry, buttys... but not like in the way people celebrate St Patricks day.
For some strange reason, the English like to celebrate that too. I hear people say "are you out tonight, for Paddy's day?". Er... no, because I'm not Irish... and neither are you. Lol