I guess maybe you missed my post? I thought I explained it quite clearly...
hehe... In other words - Google already provides a Turn based mapping app and is very protective of any app offering the same on it's wares, MAP makers also charge huge royalty's for their image file use. But... There are some open source - publically available files out there, maybe not so detailed but can do the job. That said...
Check the "GPS Underground", supposedly, there are two GPS programs which MIGHT run on the Android based handsets: IGO My Way and Navigon. I have not tried it myself, but these are in addition to the alternate method I said above. I remember also reading about a real nice commercial products that was supposed to be coming to Android by summer 2010, so we'll see with that one.
Bottom line is if you want to be able to use GPS without DATA you will have to obtain a Map/GPS app which will allow the use of stored map files. These files are not readily available just at a click, but can be gotten with a little homework and elbow grease. You will need an app that can reference stored map files, learn what type they are, get the public domain files and convert them and then hope they work... lots of work for me, but maybe others have higher tolerances for pain.
True offline maps for your Android - unplugged ! | MapDroyd
AndNav.org - Android Navigation System
Voice directions on your GPS phone: TeleNav
(not yet available for Android/HTC Hero)
GpsUnderground Forums - Unlock The Power Of Your GPS!
iGO My way for Android - The ultimate navigation for Android
(Not Available as of yet but looks real promising)
Navigon on Android -- NaviGadget
(also, not available yet, and will be first time they use over OTA navigation??? might not be what we're looking for here)
http://www.navigon.com/site/us/en/
Anyway... I would say SOON... but not right now, you will be able to do the GPS Nav thing without data. Hope this info. helps. Enjoy!