It worked fine down in that area for me last January. The only issue I have with them is how they erase your data if you don't retrieve it from their site within 3 weeks or so of it being recorded. By the time we got back from down there, I had already lost most of my data from the trip.
(note: I haven't used the device since then, so I do not know if this data retention practice is still in place. Frankly it is a significant thumbs down for this device if so.)
Other than that, the tracking function worked well with the device attached to the top of my backpack. Folks at home were able to watch our progress up the mountain quite fine.