I'm not sure on the delivery, but like all pre-paid I'm sure you can get it in hand and activate when you arrive, I think it activates when you basically connect to the network, and then would like you to register some information if I rememeber correctly when my friend did it. But she bought the one you can buy in the store (they do up to 3 month ones in stores). I've never done the 6month one so I'm not too sure.
It's Amazon, so I'm pretty sure you can get them to ship it to you in the states, you may even be able to find it on the US site, but it might be at a premium, so shipping to a friend might be easier haha. Also your US Amazon account won't work with the Japanese Amazon store.