Hi Julie, Interbus and other shuttle companies go to all those destinations and would be the cheapest option to get around. A private driver would be more expensive but give you the flexibility to stop at some attractions along the way. For the most flexibility a rental car is definitely the way to go. The roads between Guanacaste, Arenal, and Puerto Viejo are all nice and smooth too so you probably wouldn’t even need a 4×4 (depending on what activities you do). If you do rent a car, check out our page about it here, we get a really good discount for our readers. Hope you have a great trip!