I'm from Canada, and successfully ordered from Von's last year on our trip; a sweet DisBoard member had PM'd me to tell me one of her credit cards had worked - the other hadn't. Same for us! One credit card would not be authorized, and another one was authorized. We used the hotel billing addy as well. My suggestion is to try a few credit cards if you have to. BRING the one that you do end up using!!! We brought ours, and didn't need it in the end, but it's a good idea of course to have it with you.
Good luck! We were thrilled to be able to have free delivery on water, juice, granola bars, cereal, milk, etc.