Type I diabetic here as well. Since I got an insulin pump, I haven't really had to worry so much about what I eat, so I haven't really had to request anything myself, but I know it is possible. I believe if you let them know when you make your PS that they can plan to have something there that meets your dietary requirements. I dont know if they will be able to do as much if you don't let them know until you've arrived.
Anyway, bumping you up, hoping someone else can give you a little more info on this. Another place you might post your question is the disABILITIES board. There are often diabetics on there with questions about their trip, as well as other people with special dietary needs. I have no doubt they could help you out.
Sorry I can't be more helpful!
-Laura