We were at Tereza's a couple of weeks ago; you'll absolutely love it! Make sure you book for Tereza's Greek night; it's fab!
Didn't use the bus, but i think it's reliable. However, last bus into Corfu Town is 4 in the afternoon. I don't think there's an evening return to San Stef though.
We went to Corfu Town on an evening visit, with San Stef Travel (based in village). I think it cost about 12 euros each. They pick you up at 4.30pm outside Kapietanos apts (only 100 yds up from Tereza's) and you get to Corfu Town at about qtr to 6. Pick you up in Corfu Town at about 10 o'clock that eve; get back to San Stef about 11.30.
Hope this helps.