There is not a whole lot of great food near the Convention Center, though there seems to be a lot of it not far away. The Convention Center itself has some small concession stands and Starbucks. Perhaps they will be open when OOPSLA is therethey weren't both times I've visited the sight since December.
All the following places are on the other side of the Lloyd Center from the Convention Center. If you're staying at the Doubletree, you get to these places by going through the Lloyd Center (a mall (with a skating rink inside!)). In no particular order:
This whole area has lots of restaurants. The Lloyd Center has a generic food court (above the rink). Additionally nearby are these useful places nearby:
There is a burger place near the Convention Center that is probably pretty good for a quick bite: