sixtyorso was correct Bairro Alto is a good night out. It's in downtown Lisbon (Baixa) and you can reach it via the blue line on the metro - get off at Baixa Chiado and just walk out, right and uphill a little way and you'll find it. Follow the people!
Restauradores is below Bairro Alto, just above Rossio - in fact it's directly across from Rossio stationa and again, easy to find on the blue line - get off at 'Restauradores'. It's kinda round the back, if you spot the Hrad Rock Café. just walk down past there and you'll see all the restaurants.
Then there's the Expo 98 site, otherwise known as Parque Das Nações. There's some fab restaurants and a whole length of different pubs, clubs and restaurants at the North of the site. Metro - red line, get off at 'Orient'.
Or you could head down past Baixa, along the estuary (downtown) and go to the Docas (Santo Amaro Docks) - which is another set up similar to the one at Parque Das Nações. It's easy to find - underneath the Ponte de 25 Abril (25 April bridge).
The metro is €0.80 each way and if you'd rather not use the metro (which is fab by the way) then just hail a cab and tell them where you want to go - just say the name of where it is or write it down and show the taxi driver.
Have a great time - it's a beautful city :)