Please note that I have created a new thread from your post on the Sri Lanka forum so that expats members already there can help you by providing some feedback.
Maybe you could learn a few words in Sinhala to ease your stay.
You will have greater flexibility if you come alone. At the same time, be cautious that you don't get cheated by anyone. Most people are nice but you also get a few bad hats in any country. Places like Kotte, Nugegoda and Rajagiriya offer cheaper rental options. Feel free to private message me if you need more advice.