Why not get it in Japan? They have all the same models, and you get the benefit of being able to test the display model. The price difference is negligible.
Edit:
MMM makes a good point. What you'll need to use it for during your exchange is a big factor. If all you need is a simple daily-dictionary, a DS and a DS dictionary would probably suffice.
Buy Kanji Sonomama Rakubiki Jiten (Nintendo DS) - Play-Asia.com
Potentially saving you a couple hundred dollars if you already have a DS.