I was in Martinique last October. Several other passengers, without me asking, said how much the island exceeded their expectations and that they had heard bad things.
One man raved about a continental style lunch he had in a pleasant restaurant in Ft de France.
I do not know if this is true, but another passenger explained to me that France's trade policies are choking local businesses. It's cheaper to fly to Martinique from Paris than from Miami!!
As such, they have realized it is in their best interests to be welcoming to American cruise passengers. A smile and a "bon jour" served me very well (despite knowing virtually no French).
Buying things with euros was always more smooth. This IS a department of France after all.
Between the agent at the tourism office kiosk, currency exchange, 2 "taxis communes" drivers, restaurant staff, cashier at Volcano Museum (a must-see in St Pierre), young woman on street who gave directions to taxi stop, convenience store clerk, gift shop cashier, and staff of 2 liquor stores, nobody was what I would call rude. The convenience story guy charged a little premium because I paid in dollars and he could not make change....but I'm not going to obsess over a few cents.