You can't be in the Dominican Republic without trying the typical transportation. Of course, you have "normal taxis". But try the guagua, carro publico or motoconcho. They are all very cheap and funny. The "montoconchos" or "mototaxis" take you and may be another person on their motorbike for 5 pesos (10 for tourists ;-). If you think it's too dangerous, you might prefer a "carro publico" which is a cheap taxi. You might travel with 6 other people in the same car ! And the "guaguas" are the busses. The more people who get in, the more fun you have !