You should have no problem with food and drink in Spain, unless you have a very sensitive stomach. To begin with, the Spanish are not big on spicy food, and nothing they make is anything as spicy as Mexican, Cajun, Thai food etc.
Secondly, while I don't dispute the experience of anyone's stomach, I'll offer the following reassurance with regard to the dangers of salmonella from the eggs and mayo: since 1991 it's been against the law in Spain to serve homemade mayonnaise, creams or sauces made from fresh eggs in the pinchos and tapas on offer in the bars. They have to industrially-produced mayo and sauces, which have all been pasteurized, to make their dishes. Or, if they do make mayonnaise, sauces and creams themselves, the law requires them to use a pasteurized egg product to avoid the risk of salmonella. The most common product of this kind is called Huevina.
They also use Huevina to make the tortillas you see in the bars for the same reason. Revueltos (scrambled eggs), huevos fritos (fried eggs) and tortilla francesa (egg omelettes without the potatatoes) are another matter. Some places use Huevina for the omelettes and scrambles eggs too, though obviously not for the fried eggs. But they're required to cook eggs at temperatures of 75ºC or above. Obviously, if they don't store the eggs properly or cook at temperatures below this, you're can have problems like the kind falcon described above, but it's rare.
In 15 years of living and eating out in Spain, and numerous pilgrimages along the Camino, I haven't got sick once from anything I've eaten anywhere. And while I am blessed with an iron stomach and an amazing constitution, I can assure you that the food in Spain is great. And very healthy! There's so much great veg in Navarra, La Rioja and Galicia, and while Castilla and León tends to be heavy on the pork, there's loads of great legumes too. Unless you require a very special diet, I think you'll love Spanish food.