true enough. people should be growing their own, but this is a website full of travelers (fuck, the OP is about "TRAVELING and being a vegetarian) , who I am guessing are not having room for a garden in their packs. Freeganism is also an idealist diet, not about having no ideals in any way. I believe the industrial waste is a shameful disgusting waste, as are as the massive food surpluses that are destroyed every year. I am quite happy to take my part in reducing that, and in no way suporting the industry. I have also grown up with family farms, studied permaculture, and worked on various farms on three continents, in just about every ecosphere there is. I certainly would be growing my own food if I were not traveling, and even still, can often return to farms on a circuit and harvest things I have earlier in the year planted. I have mycelium patches I have spread on BLM land up and down the west coast of the US, wild crafted so I can return and harvest whenever I am around.
Sorry, this is too personal now.
Concerning the OP:
Traveling as a vegetarian is ALWAYS an option. not always a free option, and even less often an EASY free option. If you stick to the US, or western Europe, you should always be able to find plenty to eat in the containers, if you can bring yourself to "leach off of industrial waste".
Outside of this area, things get a bit harder, and you may often be competing with local people, who probably have a harder time getting the resources we have available in the western world. If you are prepared to fight with the locals, the containers may still have some to offer. You can find work on farms (in exchange for room and board) in many parts of the world, again, consider your impact on local communites (please).
Also, a bit difficult, considering the different ecospheres you may pass through in your travels, offering different food sources, but foraging is also an option to consider. There is often an abundance of food right at our feet, we have just been trained to overlook it, and head to the markets instead.
If you are motivated enough to travel, your diet will be secondary. I travelled 2 years as a vegan, 6 months as a raw foodist, and 5 years as a vegetarian (all of these mix together somehow). I was in 15 countries on 3 contients, and my diet was always fullfilled. Never once was it dictated by my locale. For the last year I have chosen to be freegan, and do not understand why I was ever anything else. I guess I dont like to define any of these things, but if I had to choose a defining word for my diet, I would call it freegan. this allows me to eat all the tasty vegan food I want, and not have to deal with dogmatic assholes who get upset when I eat some table dived peperonni pizza, or some freshly prepared veal cutlets out of the container. I still mostly cook vegan, out of respect for the other people aroune me, but wont hesitate to fry up some bacon in the same kitchen, as long as said bacon was garbage first.