The Cricket Club Cafe
The Cricket Club is a bit of an institution in Colombo - popular with expats, tourists, and wealthy Sri Lankans. It has a beer garden at the front (surprisingly tranquil given its city centre location), a restaurant in the middle, and a pub in the back. You can eat and drink anywhere with the same menu, but the restaurant is quieter whereas the back bar is usually loud and used to watch the sport on TV. Rugby, football and of course cricket usually guarantee a crowd and it's busy throughout the week, but particularly Friday and Saturday nights.
It's a great place to meet people if you're new in town. The Australian owners, Jamie and Gaby, are very friendly and the staff are excellent. The whole place is decked out in cricket memorabilia (hence the name).
The menu is mostly made up of international favourites (fish, mixed grills, pasta, chicken etc) but there are some local dishes too (devilled beef and rice for example). It's reasonably priced, with meals between 200 and 600 rupees, although this is one of those annoying places where service charge and GST is not included in the menu price, making it 25% more expensive than it seems. The hangover fry up on a Sunday morning can be a God-send!
Queens Road in Bambalapittiya, just off Duplication Road. Ask a tuk-tuk driver, most of them will know the place.