Sandals Halcyon is in the middle of the corridor between Rodney Bay Village / Gros Islet and Castries - there are lots of minibuses plying this route, service is frequent and buses run fairly late. Outside of the region, service is infrequent, the driver will wait until the bus is full or nearly so before leaving Castries for the southern regions and vice-versa. Evening service is rare. Outside of Castries / Rodney Bay / Gros Islet, I would be very hesitant to rely on the bus system.
Water taxis are the fastest way to get around, however they are expensive. I would estimate that a Castries to Soufriere run would cost in the neighborhood of $200 each way. There's not much point in going north from Castries as the Sandals shuttle will take you to the Grande, which is next to Pigeon Island National Park - it is practically the only tourist attraction north of Castries of note, besides Reduit Beach. There you can view the remains of Fort Rodney, hike to Signal Point, relax on the beach and snorkel. It is also home to a small military museum and 2 restaurants - The Captains Cellar which is an Olde English style pub in the basement of the military museum / former officer's quarters and Jambe de Bois, a rustic beach cafe, named after Pigeon Island's most infamous resident.
Edited: 22 September 2012, 14:42