1. What type and brand of sleeping pad would you recommend? $100 seems to be a standard price for Therm-a-Rest. That is a lot of money, so is it worth it?
The brand of sleeping pad isn't too important but it is a very useful item to have. We got the store brand ones from REI and they were cheaper than Therm-a-Rest ones but work just as well. The self inflating types are more comfortable than just the foam pads. Also the smaller the pad the easier it will be to carry on buses which means you will be more inclined to use it.
2. What type and brand of a solar shower would you recommend?
We have a 5 gallon one from Wal-Mart and it holds enough water for both of us to shower and has lasted 2 years with moderate use. For a single volunteer you might want a smaller one because it will be easier to fill and hang. I don't really think brand matters too much as long as it looks sturdy.
3. How formal is "business casual"? Is a nice skirt and top okay, or should it be business suits?
Lots of Jamaican women wear suits to work so you wouldn't look out of place wearing one, but most volunteers don't and wear a blouse (button-down shirt) and skirt or slacks. It is pretty easy to have a suit made in Jamaica once you are here if that is what your agency requires.
4. What kind of work shoes do you recommend that will look nice enough but be comfortable? Must they really be closed toe?
The shoes don't have to be closed toe, but they shouldn't be flip flops or Teva/Chaco type sandals. I have found a few pairs from Naturalizer that have worked well.