The best advice on hair braiding in Nassau is DON'T. Get your hair braided on the ship (deck 9 by the pools, not in the spa hair salon) or on Castaway. Both of those places are Disney controlled for sanitation, price, etc.
Our experience in the Bahamas was being accosted by all sorts of people wanting to braid DD's hair. It was $2 a braid, and I agreed to one braid (there was a sign and a place for her to sit....sign said $2. When she finished, the woman demanded $10--her hair is so long, I used beads, etc....a long litany of excuses. Yeah, I can buy the pony beads at a craft store for less than one cent each and I've never seen braids without a couple beads (that's all DD had...a total of 3 beads.) I didn't like all these people reaching out to my kid, and the $10 it cost us to get away from them felt like highway robbery.
On the ship you know the equipment is clean, and the price is clearly established in advance.