Phil,
Kind of late with this response, but if in Cupecoy to begin with and particularly on any given Sunday, I would definitely take the lowlands route through Baie Nettle and into Marigot, taking the first traffic circle into the Marigot market area and then the left at the end of the market area and keep hugging the water past the yacht club and the tanker area and finally the traffic circle that will head you towards LaSavanne and ultimately will bring you into Grand Case.
So! What route did you take? Where'd you end up? And hope your day was a good one. <img src="http://www.traveltalkonline.com/forums/images/graemlins/handshake.gif" alt="" /> <img src="http://www.traveltalkonline.com/forums/images/graemlins/handshake.gif" alt="" />