The most flexible way to get around in Cuba is by rental car. The road network is relativley well developed and almost all of the interesting places can be reached by car. Of course you don't want to compare certain issues like safety, road quality or comfort to a car rental in Europe or the States: Some roads are mere tracks and most of the time you won't be able to go faster than 50 km/h resp. 30 mph. There will be all kinds of road users, from cyclists to pedestrians to herds of cattle, and occasionally their acting can only be described as suicidal. Especially at night driving can be dangerous, and Cuban rental car companies as well as tour operators advise against driving at night.
However, there are not enough cars as there are potential drivers. This applies especially for the car categories 'van' and 'jeep'. You'll most likely get a medium or compact car. We recommend to book well in advance. Furthermore, usually only the car category can be confirmed, not the type!