I have a couple of restaurant recommendations but I'm afraid they're both on the expensive side.
http://www.restaurante100maneiras.com/
http://belcanto.pt/en/
Both are very good. They also have cheaper offshoots that are well reviewed.
If you go to Almada on the ferry during the day I'd very highly recommend Cova Funda as a place to eat. Very Portuguese and very cheap.
My favourite bar in Lisbon was the Pirata, a tiny local place near the station.
http://www.tripadvisor.co.uk/Restaur..._Portugal.html
Lisbon's great - enjoy.