Well Zipster...I couldn't reply, because... I didn't have a clue when you were coming to Cardiff... You still don't really say when... and not being THAT interested in rugby type things - (except for watching men in shorts with nice legs run around) I still have no clue about what dates the matches are actually on.
Anyways, I can't think of anything that is on around that date in Cardiff, sorry!
But as for pubs - there's loads. Nice bars opposite the Castle, (irish names but can't think right now - it's too early). All along St. Mary's street are some brill pubs too. There's a good one down the opposite end from the castle (at the end of St Mary's street) called The Prince of Wales (big bar).. Mulligans, The Walkabout.
LOADS...
Loads of clubs too! All depends what sort of music you like to dance to.
Hope that helps a little...
One thing though - will be packed full of people - further away from the Millenium stadium the better I reckon.
Regards
Ella