Cardiff is good if you know where to go, Bars like Peppermint, Mocha and Soda Bar are great PUA hotspots as they're more like bars than club, if you wanted to run dance floor game Clwb Ifor Bach is amazing as its on three floors and its alternative.
I'm a Newport native and i'm a mile away from the city center. There's a bar called Kama lounge which I consider my base to start with, great talent in there its kind of a hidden gem. As for Newport in general its know for easy pick ups mainly because there's loads of slags about. For quality women I tend to go to a club called Meze lounge, I run the majority of my game in there as everyone knows me.
As a while South Wales is drying up for using the stuff you know, people are hitting Bristol more but for simplicity I like it, i'm hitting newport tonight with a couple guys who know the game