My husband is english and I'm a spanish speaker.
When our son was born, we lived in BA for a while and then we moved to England when our son was one.
I start worrying about the language. As we were going to be surrounded by english speakers, english would be much more influence than Spanish, I was afraid that with time he lost one language and he wont be able to communicate with my family.
So I start talking to him in Spanish. All the time, I don't change this rule even if there's people around. He is 2 now, and he doesn't make sense when he talks most of the time but he started to catch some words from both languages, which it is amazing!
I found very useful being bilingual for my life and I really want that for my son. He can travel around the world easily with these 2 languages and it will be great.
We read this book that help us a lot to understand more about this subject, which I recommend because its fantastic. Its called "The Bilingual Family: A Handbook for Parents". Has a lot of examples and its very easygoing and interesting.
So if you are thinking in raise your child bilingual, go for it, its hard work yes, but it's a gift for life!
Silvina