People were renting out their houses/just a bedroom here for the football. It was madness.
If you’re looking for hotels in the centre of Cardiff, the Hilton, Park Plaza and Radisson Blu are right in the heart of everything. You can walk to most main attractions from them.
If you want something a bit fancy, the St.Davids hotel in the bay is lovely. There are also good transport links from town to the bay but you can walk it if at a push.
Personally, I’d avoid the Citrus hotel and the Angel hotel.
Enjoy your visit!