Please ignore all the advice above – except maybe P-Jay’s – and ask yourself this: Where exactly in Cardiff will your job be?
I think there is a general answer to your question, as well as a few specific answers.
The first thing to say is that Cardiff, and the whole surrounding area is fantastic. As someone who has lived in different parts of the world, and the UK, I have found few places as well suited to my personal circumstances and interests, as well as those of my family, as South Wales, and Cardiff in particular. So basically, I would strongly assert that you can’t go wrong moving here.
That said, you have to consider what’s important to you.
Do you like suburbs full of pretentious middle/professional-class English refugees? Then somewhere like Llanishen would suit you well. Why do I say this? Because as far as I can make out, most of its inhabitants are English people who came to Cardiff to study law or medicine at the University, and ended up staying. And while there is no doubt that, for a suburb, it is a lovely looking area, I would personally rather eat my own head than live there. Too far from city centre and urban culture, yet not rural either. So a pretty, but lifeless place (in my opinion). You might love it though.
I would say similar things about Rhiwbina, Whitchurch, and Lisvane. But then, if I were to be more objective, I would have to admit that there are many, many merits to these neighbourhoods as well. Honestly, there are probably very few British suburbs as pretty, and as close to the countryside and superb biking.
But when it comes to places I do like – that is, more urban neighbourhoods that allow you to walk most places, and get about the city really easily, I would say Roath and Canton/Pontcanna are brilliant.
I myself live in Canton (well, at the top of Canton; people tell me I should say I live in Llandaff or Pontcanna), and I love it. Thompson Park is about 200 metres from my house; Victoria Park about 500 metres. I can walk to Llandaff Fields in about 5 minutes, and in 3 more minutes, get to Pontcanna Fields. I have easy access to the cheap, traditional shops of Cowbridge Road, and the posh cafes of Pontcanna. The Bike Shed is a few minutes walk from my house, so it truly is my LBS, and importantly, I can walk into city centre with 30 minutes. And if I don’t feel like walking, I can hop on any number of buses than run close to my house.
It’s that kind of neighbourhood that I would choose, and I can’t think of anywhere that would fit your criteria better.
But really, even if I had to live in one of Cardiff’s less idyllic neighbourhoods, I would still take the chance. It is hard to go too far wrong when you live here.