I'm looking at a service by
Xcom Global to rent a MiFi card while I'm there. Its about $220 for the trip but says unlimited 3G data.
iPhoneTrip.com has a good service too, but your phone needs to be unlocked in order to use it, my iPhone is not, but the other two phones are.
I'm leaning towards the Xcom service so I can use it on both my iPhone and iPad, as well my laptop. Then I can just use something like Google Voice or some other VoIP service to make calls.
The downside to that is the call quality will often suck if the 3G signal is not at its fullest and I wont be able to use Google Maps to find turn by turn directions since the iPhone uses cellular coordinates to mark your location.
I'd like to not have to rent/borrow a portable GPS from someone if I can avoid it, which makes the iPhoneTrip.com service a little more appealing.