First I'll start by saying that I did eat very well in Spain. I did not go to any molecular gastronomy restaurant, but I did gain 7 pounds on the trip. The main culprit: "menu del dia".
What is "menu del dia", you might ask. Well, it's one of the standard things that restaurants have in Spain: a 3-course meal, with a glass, or sometimes a full bottle, of wine and bread (you could choose also a bottle of water if you wanted - always with no gas, unlike the rest of Western Europe). Most restaurants you get a choice between 5-7 things on each of the courses (the last course is dessert). The prices could be as low as €7 but usually in the €10 range. And those courses are not French courses with small portions. So I would always leave the restaurant way too full, but having the ability to try a lot of different things for reasonably cheap, which is what attracted me to this option.
I actually don't think that Spanish people actually eat those normally. You might see them having bigger lunches, but most of the time I saw the locals sitting in the front of the house drinking beer and just having "tapas".
Which brings me to another interesting thing about Spanish restaurants: they are usually divided into two or three spaces: the back where they have the tables and people order the menu del dia (sometimes that's the only thing you can order there), the bar area where people sometimes stand around drinking and eating tapas, and, sometimes, tables on the street where people do the same thing as on the bar, but pay more for it (some restaurants have menus with different prices for eating outside, sitting at the bar area, or standing at the bar area).
Finally comes breakfast... Spanish breakfast actually reminds me of typical Brazilian breakfast: at a "coffee shop" (that looks more like a Brazilian "padaria" without all the breads than an American hippie coffee shop), sitting at the counter ordering a cup of coffee and milk and a toast, or croissant, sometimes with jamon, sometimes just butter, and sometimes a cup of freshly squeezed orange juice.
They sit around usually by themselves (all other meals they are usually always together with a group of friends), smoke their cigarettes, watch the news on a nearby TV and have the breakfast. And in general it wasn't a very good croissant or toast, or even a good coffee. And they drink a lot of bad coffee in Spain. Always an espresso drink with machines that prepare the coffee in seconds. On the other hand, the freshly squeezed orange juice (also from machines that cut the orange in half and squeeze the juices automatically) were always quite good.
Looking back, I think I should have been more brave and mingled with the smoking Spanish at the front of the house on restaurants and had more tapas instead of "menu del dia"s. It's just that in order to try enough things with tapas it would have been better to be in a group of at least 4 people, because some of the tapas were also quite big. Oh, well... Time to lose weight again!