I used my droid in Japan, but turned off data, and only used wifi and stored data on the SD cards. I had voice CDMA coverage in quite a few places in Japan (Sendai, Kyoto, Nara, and lots of Tokyo). Dunno about the data coverage since I had that disabled.
I mostly left my CDMA voice radio on to let the GPS work better, but I had offline maps stored on my SD card, along with waypoints. No routing/nav, but you can see where you are, and where you waypoints are, and navigate the old fashioned way of figuring out where to go based on that.
I used Maverick Pro for offline maps, and downloaded google maps using atlas creator before I went.
I didn't have to bother with driving since we got rail passes while we were there, so we didn't need voice directions.
Using 3g data over there could be pretty expensive. I posted quite a bit about it on various droid forums, including this one if you go searching.
Have a good time over there, we had a blast.