What Missy said... 1000's of choices...

If you really don't like the idea of sitting alone then there are plenty of options for food-to-go. Try Shoarma or Falafel, visit one of the "Snackbars" and get real dutch french fries covered in mayo with a kroket or frikandel, try and find a "poffertjes huis or pannekoeken huis" (small pancakes or regular pancakes resp.). Many of the department stores like "Vroom en Dreesmann" or "De Bijkenkorf" have restaurants that will serve the more affordable yet satisfying food.

Try and stay clear of any resaurant that has people on the street trying to get you to come in, or those offering a "tourist meal".

If you want some specific places let me know what kind of food you like...

Most important, try and stay away from Burger King, McD's or the HARD ROCK CAFE for the entire trip, you don't want to become the typical tourist do you?

There isn't anywhere you will be treated like a pariah for eating alone. Pretty much every restaurant is friendly and I'm sure you will find something you like.