One of the best rules about surviving a convention on a budget is to avoid eating the food at the convention center at all costs. The food is all way too expensive, unhealthy, and unsatisfying to bother with. I have, at times, been desperate enough to fall for the temptation, but I'm here to tell you it's not worth it.
In Seattle this isn't a problem at all: the restaurants in the Washington State Convention Center are all common restaurants with normal prices, like the two Subways and a crappy pizza place. More importantly, though, you're in downtown Seattle--you can easily want to a much better restaurant nearby with less of a crowd.
The Boston Convention and Expo Center, on the other hand, is in a sort of desert, with nothing apparently nearby except for an expensive hotel restaurant. What's a starving con-goer to do? The answer, of course, is J.Pace and Son.