First thing I tried: GPS

The included Maps application isn't very useful in Argentina as there are no maps available. It only shows a couple of landmarks. Enters Google Maps, just to confirm my data connection was in place I opened the Internet Browser and downloaded Google Maps OTA (Over The Air). It arrived quiet fast, installed and run flawlessly. It requested permission to use the GPS, that I granted and immediately showed the usual satellite images.
If you press 0 it triangulates your position using the information obtained from cell towers nearby and does a pretty fast and good job typically missing by about 3 blocks, but wait while it positioned and downloaded the maps for the area it also was trying to acquire any available GPS satellite signal and in a moment it will accurately pin point you with a precision of 3 meters.
The GPS itself doesn't seam to put a heavy strain on the battery but keep in mind that you will be typically receiving the GPS signal, downloading the corresponding map and keeping the screen on. All that together will impact how much your battery lasts. Anyway battery is not an issue for the Curves.
Update: I am away from Buenos Aires this weekend and I had the chance to try the GPS on the road and in a small beach village called Cariló. It looks like Google Maps is not able to triangulate your position based on the cellular antennas when you have only "edge" (lowercase) connectivity. Otherwise it was very accurate (within 3 meters) and helped us through and out of the wood's dirty roads. Also when you are not getting a GPS signal the precission of the cellular antenna's method varies in rural areas as there are less towers and they cover larger distances.