First, you should always hire a lawyer before purchasing property in the Dominican Republic, making sure that he or she takes good care of the required due diligence (
http://www.drlawyer.com/txt/articlesreal.html ) Many lawyers who are very popular with brokers and sellers don't do this.
As for your question, access is not included automatically just because it is located within the same parcel as your property. The right to use a private road or path should be recorded separately on the same title as a “servidumbre” (easement).
Only in case your property has no access at all to a public road, does the law grant the landlocked owner the right to go through the adjoining property to reach the nearest public road (Article 682 of the Civil Code). The landlocked owner is expected to pay for this right.