Stress is very bad for diabeties.. so try to avoid being stressed at ALL times..

ok, I know that is not possible.. and in bad taste, but I have a had diabeties for 10 yrs so you become a bit desensitezed to someone that has just been dianoized..
SO, what to do.... Bring your own food... I do..
Low GI foods .. will get you through.
Examples of carbohydrate-containing foods with a low GI include dried beans and legumes (like kidney beans and lentils), all non-starchy vegetables, some starchy vegetables like sweet potatoes, most fruit, and many whole grain breads and cereals (like barley, whole wheat bread, rye bread, and all-bran cereal).
http://www.health.harvard.edu/newsweek/Glycemic_index_and_glycemic_load_for_100_foods.htm
http://www.diabetes.org/diabetes-basics/myths/
Most foods are ok for you too eat.... as long as it is part of your healthy diet.
If you are on meds or shots.. make sure you have enough, and then more.. always a bad thing to be somewhere and have to leave because you forgot your meds..
Take care of your feet.. very important to do that... not only because they will hurt after a long day.. but because walking all that way, will have an impact , circulations wise...
Have a great trip .......