I think, if it was me in that dilemma (and assuming that the shop in La Paz can't TIG weld or direct you to someone that could), I'd drop the oil pan and get it as clean as you possibly can.
I'd then cut away any of that jagged aluminum where the pan broke, so none of the metal was bent up inside the pan. The goal is to get the area near the hole inside the pan to be as flat as possible.
Then I'd get a small piece of 2mm aluminum if it was available, or a piece of sheet steel, and cut it to fit over the hole from the inside. Aluminum would work best, since it will be easier to shape. The piece should be larger than the hole; the goal is to be large enough to cover the hole and to provide enough room to screw the patch into the oil pan.
Drill through the patch and the oil pan and then tap the holes in the pan so you can screw the patch into the oil pan from the inside. Something small, like a 6-32 screw (or it's nearest metric equivalent, since it's Mexico). Cut off the excess length of the screws where they protrude from the exterior of the oil pan and grind them flush with the exterior surface.
After the patch is secured in place, clean the patch and the area around the patch with acetone or lacquer thinner. Cover the entire patch from the inside with JB Weld. Make sure the entire patch is covered, so the JB Weld seals the joint between the patch and the oil pan and covers all the screw heads.
Once the JB Weld on the inside is dry, flip the pan over and cover the hole in the pan and the areas where the screws come through the pan with JB Weld from the outside. The aluminum plate inside the oil pan will add a lot of structural integrity to the patch. That looks like a pretty big hole to just try and slather JB Weld over it; the aluminum patch will actually be what covers the hole, and the JB Weld will just have to seal the gaps where the patch meets the oil pan, and cover the screw heads in the patch. You could even cut a piece of metal window screen and place that in the hole from the outside; it'll help reinforce the JB Weld on the outside of the patch and make it more resistant to cracking.
All of that should seal the hole in the pan, plus have a lot more strength to deal with the bouncing around you're probably doing on bad roads down there. I think it would get you home without further issues.
Alternately, you might be able to use something like this to patch the oil pan from the inside:
I don't know if you could find a kit like that where you are, but it's designed to patch a fuel tank, so I'm sure it would work to patch an oil pan. Patching it from the inside, whether with the aluminum patch or the epoxy resin and fiberglass one, will give you a better chance of success than trying to slather something on from the outside.
Admittedly I've never patched an oil pan, and I don't know what the inside of the pan looks like and whether or not it would easily lend itself to the repair I described. But if I was standing there looking at that hole and wondering how to get moving again, these two ideas would have been what I'd try.