Yes, if shopping is something you enjoy (I really don’t) there’s loads of it – your choices are the MASSIVE new indoor shopping arcades, which have expanded to the point it’s one massive building now really full of the exact same shops you can find in any shopping place, or the little 19th centry arcades in the ‘Castle Quarter’ which are lovely, they’re amazing looking buildings.
Cardiff Indoor Market is always worth a half-hour walk around, there’s not a lot to buy for tourists because it’s mostly food, but if you’re staying with friends you might be able to make a nice meal together.
There’s a museum, which is free, St. Fagan’s Museum of Welsh Life, it’s also free bar parking – it’s a village and the various buildings are done out in various historical points.
Cardiff Bay is a lot of bars a restaurants in a lovely setting (if the sun is shining) – there’s a fun fair there at the moment too.
If you fancy I night out Cardiff City Centre might not be ideal, it’s a massive Stag / Hen do type thing, there are some smaller bars that aren’t so crazy but I’m so out of the loop I wouldn’t have a clue where to start – there’s a pattern to it – a new area / bar will open that will be popular with the local, locals, after work drinks, ‘sophisticated’ AKA a bit stuck up, then the people who live in the surrounding towns and villages will find it and it goes a bit mental, then finally the stag parties turn up and it’s chaos. If you’re not 18-25 and fancy getting wankered on Aftershock and passing out in a bin, the suburbs are better – Whitchurch, Rhiwbina, Canton, Fairwater, Penarth (different town over the water) – in fact Penarth is worth a day all on it’s own – Victorian Seaside Resort, it’s had it’s ups and downs but there’s a nice seafront (not much of a beach though) nice little cafes and bars, a Pier and lots of parks – average age of resident is about 107.
In top of that there’s the usual stuff, ice rink, cinemas, pool with a sort of splash park feel – loads of massive, very ornate gardens which are nice to cycle through.
The odd bit of Mountain Biking, in pretty much any direction to care to look, bar south – because there’s where the sea is.