I'm sure cereal bars will be easier for you, but if you're going to be staying at someone's house, get yourself some decent cereal. I'm currently in love with the Fiber One honey clusters. I eat them EVERY DAY. I don't eat them with milk. Just mix them in my yogurt (good luck with finding free yogurt). For an added punch, my breakfast consists of honey vanilla greek yogurt (0% fat) and 1.5 oz (not sure what that is in grams) of the fiber one. The protein in the yogurt and fiber in the cereal keep me going for a LONG time. There are syns in the greek yogurt - but completely worth it.
The US also does a very nice breakfast. If you can avoid the pancakes and other sugary things, you can probably find a really decent breakfast.
At the end of the day, I don't really eat a lot of convenience food so I'm probably not much help! Stock up on hi-fi bars and bring them with you. You should be able to find lots of fresh fruit and veg. Blueberries are particularly good right now!
Also, low fat cheese sticks are great. I take those with an apple and yogurt for a quick snack. And it counts as your HEXA.
I suppose by the time you have US food handled, it will be time to go home! Drop me a line if you need specifics. It really is do-able over the pond. I'm doing it!! Good luck to you!