Eating...next to drinking...one of my favorite events on the Camino. That said, one etiquette point, then a suggestion.
1. If you're staying in an albergue that includes a light breakfast...eat at the table. It's considered bad form to stuff a bag with food as you depart. You may be in a hurry to get back on the Camino, but there may be fellow peregrinos that, for whatever reason, will leave well after you. Often, whatever is put out early is all that there will be...so the later departures get no food at all.
2. I found that most towns or villages have either a Mercado...or a Supermercado. These are similar to grocery stores and carry just about everything you may want...from fruits, to cheese to hard sausage and, yes Vinotinto...wine and beer. Much cheaper here than in a cafe or restaurant.
Buen "em, em, good" Camino
Arn