I'm in the same boat as you. The code-switching is kind of freaky.... It just happens, and the appropriate language is used for the apporpriate part of the conversation, with the appropriate people who would understand. And I feel the ideas/emotions are transferred more efficiently than when using just one language. Which is why it works so well when angry and venting :).

The challenge I'm having now is doing the same with my kids. My older child has had no problem, and spoke only Spanish until preschool, but my younger one speaks in English to her sister and is having a more difficult time with Spanish...