For international travel, an airplane is the suitable means of getting to either of the 2 airports - Hewanorra in the south or Vigie smaller and in the north.
The bus system I found is very easy, however it takes some time to learn where the different buses are parked. The natives are friendly and would surely provide accurate directions if lost. The buses have a particular route that is disignated by a code.
For example between CASTRIES and SOUFRIERE that route is 3D, which would be parked at the southern entrance to the market.
Helicopter rides are available too
If you are on a neighbouring island I would suggest boat but if you live at the other side of the world I would say aeroplane.
If you are wanting to go around yourself I would definetly say hire a car. Otherwise if you are just wanting a bit of sight seeing I would say bus/coach.
Do it by sailboat - its an amazing experience. And the 4 hours or so travel time is great for sunbathing (if you can sit still for that long ;o). We ate and slept on the boat, bathed in the sea, sat and drank with a beatiful sunset ...
BOY, ARE THOSE ROADS NARROW!!!!!!!! IF you rent a car, be cautious! The roads are narrow, St. Lucians drive like any other West Indians--fast and a little reckless, the driving is on the left side (for us Americans, I know we like to refer to that as the 'wrong' side), and there are no sidewalks to speak of so there are always people walking along the road (I won't even mention the cows and the goats). But the driving can be an experience and unless you want to stay in the resort all day, you'll need some wheels.
By car (most of the roads beyond the ONE main road are very rough so you will probably need a 4x4), by bus--minivans really, taxis--plentiful and fairly reasonable.
We arrived by ship courtesy of the Dawn Princess.
We traveled by tour bus and by Catamaran from Soufriere to Castries. However, if you have more then one day to see St. Lucia I would recommend an island tour to view this great island.
Photo below show dock we left from in Soufriere.
We Flew. If you stay at the most populated end of the island you have to be bused (crowded mini buses) to the other end of the island on terrible roads. We stayed at the
club med which is right near the airport but not near the night life and sight seeing places. Very nice place if you just want a nice vacation.
The roads are narrow and full of pot holes and curves. Very scary to drive. If I went again I would hire a driver to take me to the out of the way places.
We woke the morning to a lovely view of St Lucia with the picture perfect twin PITONS being the identifying mark of the island.