What company is taking you to Negril? Is it a shuttle from Grand Pineapple or another company?
If it is a JUTA shuttle you may have to wait around for other people to arrive before you set out to Negril. You will also stop at other hotels to drop people off before arriving at G.P.
IF it is a G.P. shuttle only, you may have to wait to pick up people but you would go straight to the resort...
When exiting customs walk straight out and a little to the left and someone will help you find your ride...