Buses are available in Northern St. Lucia, around the capital city of Castries and at Gros Islet. Bus service runs till about 10:00pm, and a little later on Friday nights. However, there is no scheduled timetable. Far from Castries to the north coast area is from EC$1.50-$2.75 , and from Castries to the south is EC$7.00.

The local buses are good value for money, and all fares are in EC currency. Try and have the local monies instead of the US dollar or you will find that some drivers will over charge you or charge you the fare in US dollar.Other than that it's the cheapest way to travel and there are many buses from Rodney Bay to Castries route.

http://stluciabus.wix.com/lucia 

Visitors can also take taxis, which is pricier but it is what it is. They are available at designated taxi stands, while cabs can also be called for pickup by telephone. Minibuses, which can accommodate up to 10 persons, can be hired as taxis for small groups. Taxicab fare from Castries to Hewanorra Airport is about EC$120 (could be has high as EC$160 one way from the airport in the north to the international airport in the south), and from Castries to Rodney Bay is about EC$40. Up to four persons can ride for the price of one.