Just finished a month in Santander studying Spanish. Thanks to those who made suggestions. For various reasons we did not do the highest end places (eg El Puertal) but did eat well at what by Manhattan standards are moderate prices. We mostly ate pescado rather than mariscos. All the places we ate at served only a few fish on their menus, given the season and what appeared on the fishing boats that morning. Typically cooked simply (a la planca or al horno) and always was good. And my first experience of chiparones, which I loved.
Our favorite resto was Bar del Peurto, which had a great combination of wonderful fish and a very nice atmosphere (though I did find out the hard way that pantalones are required there, even in Agusto). The fish soup was wonderful.
We had very nice meals at the bottom of Tetuan (about 4 small places in a row), and the more upscale La Mulata across the street. Other than getting tired of pescado, all were just fine (none fabulous, but we were neither expecting or paying for that).
We were staying in Sardinero, so we ate a few quicker dinners at Canadio(?) right near the beach (Juan de Costa?) which was more than acceptable. We also had very nice paella (marisco of course) at Los Infantes on the street of the same name.
Lots of good pinchos for lunch on General Mola and Pena Herbosa and other streets near Saez de Sautoloa.
In short, we ate quite nicely, though nothing really exquisite. But I would have been happy with almost all these dinners (at that price) in Manhattan on all but the most special nights. And I love the price of the rioja which made up for the weak dollar.
Thanks again for all the help.