If you are stopping on the Dutch side at Philipsburg I believe it can take as little as 20/25 mins. However if there is a lot of traffic it can take a lot longer. When I went a few weeks ago the cars crawled along at a snails pace until we reached the junction. make sure you allow yourself plenty of time when you return.The taxis leave from the Sunset Bar & it would be a good idea to ask one of the drivers what time to leave to get back to the ship in time.I believe they charge $8 per person in a taxi and they have some larger ones as well.
you may want to do a google search for flight schedules, I think the large flights from the mainland tend to land after 11am. Watching the little island hoppers land isn't as much fun. THere's actually a sign at the Sunset bar with the flight imes on it...should have taken a picture!
We never used a taxi but check on the flight departures and arrivals before you go. The last time we were there around 2 PM we missed everything & had to start back to the ship. I've never see a time where there wasn't congestion on the way back to Phillipsburg so leave at least 1 hr.
I just returned from Maho Bay. We did the trip twice b/w Philis. (Port) and Maho via Bus. It cost 2$ per person and it took anyhwere from 25-35 min. The larger flights come in 11am or so, and later in the evening, around 5-7pm.
The last time we were there in November of 2011, we tried to take a taxi to Maho Beach, but they told us that there was construction on the road and that it could take well over an hour or longer to get back. We decided not to risk it.
Also...don't be a goob and hold on to the fence at the end of the runway to see if you can withstand the jet blast from airplanes taking off. Google 'blown away in st maarten' and you'll see. A recent episode of injured fools is currently on many news websites.
This was featured last evening on a program (can't remember the name) relating to scary aircraft landings...That beach seemed a lot smaller and the planes really close to the people on the beach and the vehicles driving by between the beach and the airport fence.