It's near the Boralesgamuwa Lake. You can take High Level Road to Maharagama and loop back around, or take the 120 bus road and turn onto the Maharagama Road. Go till you get to the Lake and turn down a little lane near the end. Look at the map.
Good place to try Sri Lankan Chinese & Chopsuey.
Nice, cosy café with nice, recycled furniture and a shaded…