I wouldn't recommend the airport for the reason given by Cubsur!
However, at Sete Rios Bus Station, if you follow the signs from the Bus Station for the railway station you will go down a flight of stairs/escalators. There is a small alley that the taxis use.
Turn left along there and go through the short tunnel.
About 50 metres along on the corner there is a good cafe that does lunches for local office workers.
Food was good and not to expensive, last time I was there a few months ago. They probably to coffee and toast/crossaint for breakfast as well.
