Bottom line - Plug-in and Talk.

I have used my Vonage ATA all over the world to give me a US telephone number (in and out bound) wherever I am. I really don't care what my IP address is, and the ATA handles telling the Vonage servers. (otherwise it wouldn't work, right?)

I carry a small travel router so I can use both my PC and phone in the hotel room at the same time. This way if there is some sign-on required to the hotel internet, it can be done on the PC. You want your phone plugged in all the time if you want inbound calls.