agree - but take care with cycles - they often get stolen there.If you like cities, there is a city centre campsite in Cardiff.
Cardiff caravan and camping park - Cardiff caravan and camping park
Cardiff Caravan Park is situated in beautiful parkland. An ideal base to explore the attractions in and around Cardiff.www.cardiffcaravanpark.co.uk
Not cheap but so well located.
Cardiff site is easy enough to get to, castle and parks are good. Some interesting arcades with independent shops. Bay Area good for a stroll and the white water rafting is fun. Can take a water taxi from castle to bay.
Personally think Wales is more about countryside though - so Pembrokeshire, Gower, Brecon or central.