Deb2k4,
I am jealous that you are going to Sosua on new years day while I am trying desperately to find a way of getting there for new year!!!!
The weather is generally hot and sunny, but there is more chance of rain at this time of the year. In fact, it is raining in Sosua as I speak. Don't worry, I was there last week and a little rain never stopped me doing anything. Make sure you pack a little umbrella in case!
I changed my money to dollars. You get 32 pesos to the dollar. However, if you take english pounds, you get about 54 pesos for one pound. You can change either in Sosua, and there is a cash machine to get money from if you run out!! Don't take pesos before you go, keep dollars or pounds and change them to pesos as you go along. Remember to keep $20 for coming back at the airport for taxes.