Tek,
I can't help you with the MotionX Drive, but MotionX GPS allows you to download maps onto the iPhone / iPad. You can use this app to navigate around a city -- not for turn by turn driving directions, but it will show where you are on individual roads.
The nice thing is you draw a circle on the map and then choose the level of detail for the download. The more zoom levels you choose, the bigger the file to download. I am going to Europe this summer and have downloaded several city maps (Barcelona, Rome, etc.). Barcelona was about 39MB and I loaded the zoom to 17 of 18 levels. I chose down to the street level detail -- will be great for walking around and finding our way. I can have cellular data turned off (so no international roaming) and the GPS will use the downloaded maps to show my location.