That would be a dynamic IP of the telco provider network - not much you can infer from that.
But you can use the network location provider if the user has enabled that. That's what the ACCESS_COARSE_LOCATION permission is all about (as opposed to the ACCESS_FINE_LOCATION which covers GPS). As usual, the Android docs have all the details: http://developer.android.com/guide/topics/location/obtaining-user-location.html
need to spend time reading through the documentation, most of your question are answered right there, even with code examples.