I did a day trip to Santiago, DR's 2nd largest city.located in the north-central part of the island. DR has highways linking its major cities and I reached Santiago in 2.5 hours on a Caribe Tour bus (D$250 or abt S$10). Walked around the city for a few hours visiting its huge Monument for the Heroes of the Restoration, churches and Fort San Luis.
Also bought a bus ticket to go to Port-au-Prince in Haiti on Monday. The one-way ticket costs US$40 plus US$26 departure tax.