Harsh sun in poor places
You also might want to consider hiring a local photographer (recomended by the local group)--these days there are talented and experienced people almost everywhere. One advantage is that the person can document your interaction, not just the client in isolation.
This is actually an *excellent* point, though probably not the answer the OP was looking for.
I once thought that this was a little narcissistic, but I must admit that it makes all the sense in the world.
I recently went on a trip to China and we went to my wife's hometown - a small island called Gulangyu.
Fortunately, I had an uncle in law that was willing and able to take pics of my family.
I handed him my D200+ 24mm F2.8 combo. It was the first time he'd ever seen, let alone use a DSLR. He had experience with film slr.
There was plenty of light and I just made sure that the camera was set the following:
- single point focus - center point
- P mode
- ISO = 200
- RAW only
No works of art, but INVALUABLE for capturing my memory with my family at that special time.