get Osmand...a good GPS app wherein you dont need a data plan to use it.
You just need a GPS signal and download the maps to your phone or tablet.

It has offline navigation using only GPS.
it might now show the best route like using EDSA on a weekday during rush hour but it will surely prevent you from getting lost.

You can have the entire philippine map for only 50 mb...comes with voice navigation too...

farthest i've used it is up to Batangas... so far so good