That hotel is a fair distance from the train station. There are two restaurants nearby. Restaurant de l'Ocean which is mostly seafood at the far end of the beach and the Valencia. The Valencia has new people in the restaurant so I don't know it enough. If I were you I would head up to the centre of the beach area (towards the tourist office) and go to one of the streets behind the beach to get a bite to eat. You can also contact refuge Wallon at firstname.lastname@example.org
Jerry, there is still a lot of snow. If you remember the Petit Train d'Artouste, it was on the news the other day and lots of snow still there between 1300 - 1600m. It is getting warmer but it could still be risky 10 days after you start. I do know of some people putting off the start of the trip until the end of June to be sure.
The link posted by Ed is of no use now. It is only updated during the ski season. Once the skiing is over that is it for snow reports by Meteo France. Your best bet is to send an e-mail to one of the refuges just before you leave.
Don't know where you will be staying but in the centre of town there is a gite exclusively for walkers and cyclists on the rue Fontain which is about 13 Euro the night. It is above a bar and then nearby there a couple of restaurants which aren't to pricey but all closed on a sunday evening at the moment. If you are staying down near the beach then there are plenty of places but they are mostly fish restaurants and more expensive.
This information is probably out of date but Heinrich Harrer who was the first person to climb the North Face of the Eiger had this same problem whilst living in Tibet. He said that the hot springs were excellent treatment. In Germany, France and other countries Europe etc this is still a 3 week treatment paid for by the health service. By a Jacuzzi/hottub. When they were invented they surely weren't devised just for porn
Potes is your best bet as it is closest to Santander. You could also go to Cangas de Onis the other side of the park which is quite close to Llanes, has the roman bridge and is close to the Lagos de Covadonga which is also worth a visit. Arenas de Cabrales as Cathy says is fine but a little smaller, and maybe a bit too remote for Two teenage girls.