We spent a month in Martinique last year. Tho we were on our boat, we did rent a car. Road maps are easy to follow.
Definitaly bring some sort of French/English translation source. We found in Restaurants that had wifi, we could use Google Translate on my Iphone to translate what was on the menu.....to a degree. LOL
If you ask for wifi, ask for WeeFee.
There are a number of nice restaurants along the waterfront in Ste Anne. There is a hotel south of Ste. Anne called Le Caritan. There you could snorkel/swim. It is south of LeMarin.
If you plan to bring cash, be sure to change it before you get there. We only had a few Euros and a bunch of US cash. We could only find one place that changed money and that was in FdF.
We always felt safe in Martinique and the people were very friendly and tried to help as best they could.
Our funniest experience was to ask if they spoke English and they would reply "a little bit". Actually those were the only words they knew. LOL
Also, in Ste. Pierre all the signage and info about the volcano is in French.
Next time we go, it will be with someone who can understand and speak French. Hopefully that will be soon!