I agree. Uber is pretty good in not just Sri Lanka but other parts of Asia as well. Buses and trains will be quite cheap as well. I don't think it's wise to hold off on hotel reservations until arrival...too risky. What if you don't get good rooms. Trains are a great way to move across the country. They're an economical option as well. As a lover of history and mythology, I'd recommend, if you have time, to try exploring the "Ramayan Trail" in Sri Lanka.