If you are not a seasoned DR driver I would take the main highways to Santo Domingo and then pick up RT 7 which is the Santo Domingo -Samana Highway North. This is out before you reach Las Americas Airport. Where on the Samana Peninsual are you going? If you are going to Samana City than you pick up Rt 5 where Rt 7 ends and take a right going east. Follow this road all the way. This drive is probably a minimum of 5.5 to 6 hours.
If you are not a seasoned DR driver I would take the main highways to Santo Domingo and then pick up RT 7 which is the Santo Domingo -Samana Highway North. This is out before you reach Las Americas Airport. Where on the Samana Peninsual are you going? If you are going to Samana City than you pick up Rt 5 where Rt 7 ends and take a right going east. Follow this road all the way. This drive is probably a minimum of 5.5 to 6 hours.
It doesn't sound like you are familiar with Samana City. If you want nice beach and activities I would suggest you go to Las Terrenas not Samana City. In Las Terrenas stay at the Hotel Colibri or Hotel Aliesi. They both are located across from the beach.
