The best way to get around Curacao is definitely by car rental, as public transport is few and far between. You can walk around Willemstad, but you definitely need to rent a car if you want to explore outside of the city.
We booked our car on Discover Cars before our trip. They’ve consistently given us the best prices and service. Car rentals in Curacao are affordable, at around US$25-30 per day. We spent around $400 for our 2-week car rental.