Be in for a shock, I had no idea what to expect when I went, but its a poor poor place, roads are bad and there really isn't any infrastructure or economy that I could see, very sad to see, that a place which is a mecca for divers isn't more developed - but its lack of political will and the way things 'are done' 
The only building work that was going on - at all! was a brand spanking new church for the later day saints, which looked so odd as everything around it was a mess.
I really wouldn't venture out alone, umemployment is high and with that crime from what I understand. I would make sure you have VERY sufficient travel insurance, as healthcare on the island isn't the best, so you will need to be flown out if needed.
Where are you staying land based or live aboard? I've stayed at Blue Lagoon and all the staff were very friendly, food was good and the rooms clean and tidy - alas it seemed like a world away from the town down the road. The following week we were on ThorFinn and again all the staff were good etc
It was an odd feeling, I mean all the staff were friendly and the food great, but it did feel like you weren't really welcome.
Money is USD, prices are okay (if anything, there are similar to anywhere else in the world) - from what I remember there was a 50% tax on alcoholic drinks, and all the prices with plus this, plus that.
Its hot - and humid, Shorts and T-shirt is way enough. Water was 28-30'c - really warm.
Obviously keep away from drinking the water and if you aren't used to the heat, some water additives (for salt and mineral recovery) are a must. Only drugs we needed on the trip was some decongestions, as after 8 days of diving peoples ears were starting to play up not equalising etc.
Going back in November! (As the diving was so great!)