Best countries for young single tourists?

[Lisa]

My cousins and sister and i are deciding on where to go on vacation next July and we've been thinking about Puerto Plata in the Dominican Republic but we aren't 100% sure about that yet. What are some good countries to visit and can u give specific cities in them. BTW no suggestions of Jamaica please i've been there twice already and even tho i loved it i want to go somewhere new
i"ll be 18 by next July my sister is 24 and my cousins are 22, and 21