Coming back to Rua Garret. Go up to Largo Camões, one of the most famous Portuguese Poets. Actually on the way you should bump into Fernando Pessoa, another really famous poet, right in front of the coffee shop Brasileira. The word bica, which stands for expresso, was born out of the acronym in the posters in this coffee shop saying Beba Isto Com Açúcar, which means, drink this with sugar. If you are actually looking for sugar go next door and try the amazing chocolate croissants in Bernard.
In Praça de Camões, to your right you have Bairro Alto, night out place with tiny bars and cheap alcohol, also with good pasteis de nata in Manteigaria. Try BA Wine Bar for a wine tasting session with great boards of cheeses and chorizos. Or go to Cabaças for "Naco na Pedra" (make your own grilled beef) or to Casa de Fado if you didn't do it in Alfama. You also have São Roque that I mentioned above. In front of you you'll find the last hill, Santa Catarina. Good references are the rooftop Park, and the restaurants around the square of Adamastor. If you keep going you may end up in the Parliament, beautiful building, just imagine all those stairs full of people doing a demonstration against Troika if you are new buy go and have the best beef in Café de Sao Bento and very nice Ice creams in Nanarella, some say it's even better than Santini so have both and let me know.
Coming back to Praça de Camões on your left you have Bairro Alto Hotel with a nice bar on the last floor top but bit expensive and if you go down the hill you
get to Cais do Sodré. On the way you have some new places like Palácio Chiado (with fancy restaurants), Pensão do Amor or Espumantaria, worth a try. For cheap drinks in Cais do Sodré try black Tiger or Solar. As for food go to the market that sponsored by Time Out, called Mercado da Ribeira, similar to Mercado de San Miguel, if you have been to Madrid. Try Croqueteria and Bolo da Marta in Nós é Mais Bolos.
To go out until morning in this area with good techno music choose Lux.