This has got to be one of the biggest problems many people encounter when trying to get into or stay in shape: Traveling and eating healthy. I'm not going to lie and say that it's a breeze to do. It takes some thought and some know-how. I travel a lot for work and I still manage to eat reasonably well in spite of this hurdle. I'll admit that some of the things here that I mention have some downsides but you have to look at the alternatives: Junk food.
The easiest healthy food to find on the road has go to be nuts, seeds, and peanuts. Even the most junk food-laden cornerstones and airport gift shops have them. They are loaded with protein, minerals, and healthy fats. Since they have a high fat content, they make you feel full with less fuss. Now, the fat content may be a bit of a problem so just keep the quantity marginal (an ounce or two will do). One other drawback is the salt that they throw on. Keep your eye out for unsalted or better yet, unroasted. Like I said, they're way better than candy bars and chips.
Not-from-concentrate juices are getting surprisingly easy to find. Look for ones with no added sugar. Cornerstones always have milk. In airports, milk can be tricky to get a hold of though. One option that is getting easier to find are juice smoothies. Many airports have them now. They are expensive but they are a good way to get some fruit in on the quick. Even when I can get to these beverages I still drink a lot of water. That is never hard to find.
Now, I know that you can get sandwiches and salads when traveling but I generally avoid them since they are often loaded with fatty dressings, aren't very fresh and therefore don't taste good. I may sit down for one but for anyone whose traveled, sitting is a luxury that you often don't have. Food has to be portable and quick to eat.
Ultimately, when it comes to food and travel, the 7 P's come into play: Proper Previous Planning Prevents Piss Poor Performance. Bring your snacks with you. Pack raw, unsalted nuts and seeds. Dried fruit works well too. Fruit and nut bars like Larabars (Http://www.larabar.com) are great on the run. A huge advantage to packing it is that they're WAY less money than cornerstones or airports. I recently bought 10 ounces of pistachios at an airport for $14.00.
This is hardly a comprehensive guide to eating right on the road. It's just what I do. You can eat right when traveling but it's just going to take some thought. You need to ask yourself if what you're eating is good for you before you buy and consume more often than you do in your normal, controlled surroundings. It's a bit harder but it is doable.