This is from another thread I replied to on the subject.....it is a few years old but it gives you an idea.....
As far as taxis go, try here:
St. Martin Taxis | stmartin-guide.info
Just one possible scenario, you think you have plenty of time to get back to the ship (even if you get lost), but are not aware of the traffic backups due to the drawbrige opening times, you miss your ship.
The taxi driver would be aware of these things and be able to advise you accordingly. Between Cupecoy and Phillipsburg, there will be a drawbridge opening at 5:30 p.m. that backs up traffic.
Rush hour traffic to Philipsburg maybe starts pretty heavy anytime after 4p.m.
Rates are slightly different depending on which side of the island the taxi is based, though both Dutch and French cabs service the entire island. St. Maarten taxis have minimum fares for two passengers, and each additional passenger pays US$4 extra. One piece of luggage per person is allowed free; each additional piece is US$1 extra. Fares are 25% higher between 10pm and midnight, and 50% higher between midnight and 6am. Typical fares around the island are as follows: Queen Juliana Airport to Grand-Case: US$25 for up to two passengers and all their luggage; Marigot to Grand Case, US$15; Queen Juliana airport to anywhere in Marigot, US$15 to US$20; Queen Juliana Airport to the Maho Beach Hotel, US$6; and from Queen Juliana Airport to Philipsburg, about US$15. The airport tothe Princess casino in Cole Bay is US$12.
St. Martin taxi fares are also for two passengers, but you should plan to add about US$1 for each suitcase or valise and US$2 for each additional person. These fares are in effect from 6am to 10pm; after that, they go up by 25% until midnight, rising by 50% after midnight. On the French side, the fare from Marigot to Grand-Case is US$15, from Queen Juliana Airport to Marigot and from Queen Juliana Airport to La Samanna, US$15.
The fares on the island are not metered. Always ask what the fare will be before departing for your destination. That way, there will be no surprises!
Driving around the island is not difficult and really no distance between places is very far. The daily car rental may be equivalent to the cost of using a cab so it is really a matter of convenience. A cab will also give you a bit of a guided tour if you are not familar with the island.
If you rent a car..DO NOT LEAVE ANYTHING IN IT OR THE TRUNK.
Phil & Liz