On one trip our friend and driver Niah picked us up to return to MJB and our flight home. As we were leaving Negril he somehow learned about a tag check farther up the road and his van had an expired tag (brake tag, JUTA decal, i don't remember.) So instead we headed off in the opposite direction to the airport! And that is how my wife and I got to travel the route you're discussing. As I recall it did take a little longer but we still made it to the airport on time. After our about face we left via the backside of Negril and soon headed off into the hills. As we started to climb, traffic began to melt away. Cottages and cabins were few and scattered and all seemed to hang precariously on steep hills. There were lots of switchbacks going up and then back down, featuring vista after vista. And green verdant green in all directions! I don't know the elevation there but it was noticeably cooler at the top. So if you've got the time and a few refreshments it's an enjoyable ride.