Since you reference McDs, there are fast food options that are better for you -- some of the sandwiches at Subway or Panera, for example, or a grilled chicken sandwich from a fast food place. I've read that roast beef is not a bad choice, if you're near an Arby's, and they also have turkey sandwiches on wheat bread. And the last time I was at Wendy's the guy in front of me ordered a chicken salad that actually looked pretty good.

If you've got a fridge, why not bring yogurt and cottage cheese and a giant pre-made salad, or buy some at a local store after you check in? For breakfast, a healthy cereal with low-fat milk or oatmeal should be doable.