Tekamthi
Newbie
just to clarify, you only need data for loading maps, not the GPS itself. you can also load up maps while on wifi and use them (with GPS) without a data plan. i just reposted and article about this here.
doing the above is a true travel superpower... takes a little tech-literacy maybe, a small budget for extravagance, and some care in the field not to smash your device, but well worth the trouble