I live in Granada, and I have always found an offering of vegetables, cooked well and in various ways, at restaurants. I think where they may be more likely dismissed is in tapas bars, but even there I have been served roasted pepper salads, pisto, and remojón (a delicious salad of bacalao/cod, tomato, and oranges). In the menú del dia, which is usually a 3 course meal in the middle of the day (lunch) ranging between 9-25 euros, I have always seen various options of vegetable dishes, even plates where they are the main focus- gazpacho, grilled vegetables, salmorejo, fried eggplant with honey or molasses, stuffed piquillo peppers, etc. From my experience and people I have spoken with, vegetables in Spain are highly regarded and there is a lot of respect and demand for fresh ingredients in both domestic and professional cooking.