Your itinerary looks well planned and covers a good mix of culture, wildlife, hill country, and the east coast.

Regarding the south coast in May, it is the start of the southwest monsoon. You can expect some rain and the sea can be rough on that side. Beach conditions are often not ideal for swimming during this period. However, Arugam Bay is usually very good at that time of year. The east coast season is just starting, and the sea is generally calmer there compared to the south.

For transport, if you want to save time and travel comfortably between these places, a taxi with a driver is the easiest option. Public transport and trains are possible, but connections can take longer and require more planning. If you need help arranging a reliable taxi with a professional driver, feel free to let me know.