I use Route 66 with a bluetooth GPS receiver. I had this setup on my Moto Q (it doesn't have a GPS receiver). It doesn't require data since it's pre-loaded maps. Has turn-by-turn navigation too. The only gripe about this is that the maps aren't always up to date.
The annoying thing about Garmin is exactly what bfaber talked about. I have a lot of stuff on my personal microSD and having to swap all the time =
