If you blink
The turn off is just past the toll booth on the our skirts of SD. This is the toll booth you do not pay at as it is for out going only. The turn is a left side exit that is poorly marked. I have driven it both night and day and have never had a problem. Have them buy a current road map and they should be ok
Good luck.
If you are coming from the east on Las Americas the turn off to Av Los Palmeros (the parallel road to Las Americas) is on the right after you arrive to the toll plaza area, about 200-300 meters beyond the booths. If you blink you miss it, the signage is very poor. More money is spent on huge political campaign signage you can't miss.
Los Palmeros brings you to the entrance of the Autopista del Nordeste to head to the north coast. Even for the seasoned driver in the DR access to the road, Los Palmeros, is difficult.
The country spends millions on new roads yet does not have the common sense to create signage on approaches to important intersections to direct traffic. The again, signs are destroyed, stolen, or hidden by overgrowth. Welcome to the DR.
Regards,
PJT