Portuguese speaker here! DD is 16months and is learning 3 languages, Portuguese, Turkish (DH's language)& English. We adopted the method of one parent, one language (a bit difficult for us sometimes - we speak English between us) English was introduced in the nursery at 6 months. It seems to be working well, it has not delayed her speech at all. She does understand either language, but most words learned seem to be Portuguese. We do talk a lot to her, describing what we are doing or what is going on. We give her time to "talk" and respond to her babbling, as if we are having a two way conversation. We also read a lot, she loves books.If we read to her in English, we always name the pictures in our language. Her favourite at the moment is a portuguese book, written in rhyme & quite long. Not a baby book but she loves it. I have found a book with traditinal portuguese children songs and games, it brought back a lot of memories as a child, and I am brain washing her with it! I think Portuguese is difficul to learn, there are a lot of sounds that, unless she learns them now, she will never get them right, so I try to be consistent.
Sorry to go on a bit but I hope it helps.