Stayed here with my partner for a week in May 2013 to visit a friend in Oviedo. Hotel is well-located: only a 5-minute walk to the main shopping district, 2 minutes from the train and coach stations, and near two supermarkets.
Neither I, nor my partner, had any Spanish, so found it a bit difficult communicating with staff, particularly the night porter who was on desk when we checked in! Thankfully our friend could translate! Having said that, staff were very friendly and more than happy to help us.
Despite having paid for breakfast, we only had it once, favouring instead a trip to the supermarket, Alimerka, around the corner to buy fresh bread, ham and cheese. The Spanish don't seem to do the whole breakfast thing; instead, they have very late dinners (it wasn't unusual for us to eat at 11pm). The breakfast served in the hotel consisted of cheap orange juice and processed yoghurts (maybe it's a cultural thing!)
The room was small, but perfectly adequate for what we wanted, i.e. somewhere to sleep, and spotlessly clean. The bed was comfortable, but the housekeeping staff didn't change the sheets for the entire week, and considering it was warm and humid at the time (at least for an Irish person!), the sheets smelled a bit by the end (disgusting, I know, but I thought I'd give you lovely people the heads up!) There was a flat-screen TV on the wall, which had no English channels (normally you get at least CNN or BBC World Service in European hotels).
Bathroom was small, but again, fulfilled our needs. Shower had fantastic pressure and was great after a long day of walking around in the sun.
Overall, I'd return to Hotel Carreno!
If you come to Oviedo, do make sure to have a day trip to Gijón, a lovely seaside city about 30 mins away. Return train is only €6.00. There are some fantastic places to eat and drink in Oviedo too, make sure you wander aimlessly for a few hours in the city centre to discover them! Just make sure you bring a good phrasebook/dictionary. We found that very few locals, including young people, spoke English. Having said that, they were very friendly, and were enthusiastic to understand what you were saying! I'd advise against randomly ordering things from menus you don't understand--we almost ordered octopus ("pulpo"), not something we expected!
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.