Not to mention with the time difference, you'd be up in the middle of the night trying to call!
Are you using a travel agent to book your trip? If so, they should be able to make your ADRs for you. Probably using one that specializes in Disney would be the wisest choice, because they'd have a clue what an ADR even was.....this website is sponsored I believe by DreamsUnlimited.... and MouseforLess.com is another good reputable agent. Both of these companies will constantly monitor your package and automatically get you any deal that comes along that will save you money.
Otherwise....you might try emailing disney and explaining the high cost of an overseas call and see if you can give them your 1st/2nd/3rd choices if they'd do it by email. I've not heard of anyone doing this, but it's worth a shot.....we are always hearing how Disney goes the extra mile for their guests....put it to the test.
Last thought....do you have any friends here in the USA? Maybe you could be on Instant Message or email with them and they could do the calling for you. By you being on IM or email with them, then if a time you wanted isn't available, they could quickly communicate that you and get your opinion on the times available or second choices, etc. I'd say the majority of people in the USA don't worry about long distance (within USA) calls because we all have cell phones with free long distance (i.e. it only costs minutes like any other call, not extra for being out of state). I know in my case, I have a calling plan that gives me 5 "friends in my calling circle" that I can call for free. I can change them as often as I want.....they take affect the following day, so I just load Disney's number in the night before and voila, all calls to them don't even count against my minutes!
Good luck!