Hi,
I'm probably the one who posted that you don't need a gps on the Frances. It is true, but I can totally understand why you might want one. With a good unit you can record your entire trip, and later go back and find exactly where that nice little bar was, where you went off trail to take a picture, how long the climb to O''Cebreiro took etc.
First, Garmin makes wonderful units, but their software, and particularlary their unlock process has been described as "the worst in the history of the planet". I have never loaded a map without calling service, but I don't feel bad, because IT professionals have told me the same. Once you get your maps unlocked, things go much better.
We have two small units, a Garmin Dakota 10, and a Dakota 20. Garmin is correct in that neither could hold the entire map of the US and Spain in internal memory. I think either would hold the entire Camino and your home state, just not the entire country.
The Dakota 20 has a major advantage in that it will accept a micro-sd card. These are nice in that they just pop in without unlock codes and add the map, so you could have the US in internal memory and add the Europe SD card when in Europe. It is a great little GPS, and not too expensive. It definitely will record an entire Camino, right down to what bush you went behind to pee.
Garmin also does something I consider outrageous. If you buy the cd of a map, you can only load it onto one unit. If you lose that unit or upgrade, or buy one for the car and one to hike with, you have to buy the entire software package again. It is no wonder that when you google up where to buy a Garmin map you find more pirated versions for sale than legitimate ones. Send me a pm for more raves on what I consider ethical and how I manage my maps.
A great website is GPSFileDepot. Also
http://www.velomap.org/. They have all sorts of free maps and tutorials on installing and using them. I've downloaded a nice map of France, and topos of the western US for free from them, and they install much easier than Garmin's stuff.