I live in Guatemala and my husband is Guatemalan. What we found worked best is to separate the languages. My husband speaks Spanish to our sons, I speak English to them and we speak Spanish to each other (my husband isn´t fluent in English). Also, to help boost the English, we bought some DVDs of Hi5 and my toddlers favorite movies in English. He speaks and understands both languages without any problem and my 10 month old is already speaking words from both as well.