I can't really help with stores in that area, as I'm on the West Coast, but about the bread on the plane thing. You can bring it in, as long as it's for private consumption, and you won't be selling it or trying to promote it as a product. So a doctors note might help with customs if you plan on bringing alot of food with you. You also won't be able to bring in anything "fresh" like fruit or part of a plant, something that mihgt contain bugs. I have alot of international friends, so I've dealt with this alot.
That said, There are Whole Foods in many states in the us. Also, for dining in the US, most places that don't offer a gluten-free menu are pretty clueless. Dining cards are really helpful, and sometimes even help ME remember what I can't have. I recommend the triumph cards : www.triumphdining.com. I have those and LOVE them.
As the waiter said to me on Thursday night "oh this is so cool that you have this" (talking about the dining cards).
As for what products in the US are gluten-free, if you PM me with your email address I can send you the Delphi list in either word or .pdf format. Its not everything, but its useful in a normal supermarket.
Have fun

Elonwy