Originally Posted by The Chief (tm)
Nah, all good advice, even for your current lack of a PC...
I did, in fact, check what was on the SD card I'm using now (for North America), and it was a mapsupp.img (or whatever) file -- meaning, it has the same name. I thought, "Oh, why don't I just swap them out and see if the GPS recognizes the new maps," but then I realized that I'm not in Mexico right now, so there wouldn't be any way to really "test" the swap, right?
Although now that I think about it, maybe I could ask it to find a location somewhere in Mexico, and if it returns a list of possible choices (for city name, street name, hotel name, or whatever), then that *should* mean that it's reading the new file correctly, even though it probably couldn't create a route to it, 'cuz it wouldn't "know" where it was right now here in the States. I'll play around with it.
But the point is, it was helpful to know that all I needed was that .img file. Thanks for taking the time to clarify!