Second the post mentioning Bavaro Express, and there is another bus company in the country as well that does long hauls, both will cost $5-10 to get you there. Ive been to Dominican twice and was also told that the expensive taxis were the only way, but knew that that couldn't be right! The big buses are comfortable and air conditioned. The local transport is also an option for long or short hauls, they will just take longer to get there. They are called "GuaGua's", and can range from the back of a pickup truck, a mini-van or larger passenger van. They are cheap and run during daylight hours only. As a single woman traveler they got me everywhere where I needed to go across the countryside and the drivers were always nice and made sure I got into the next transfer on my route easily!