Can monolingual parents teach their children another language?

No. If you do not speak Spanish fluently, you cannot teach your child Spanish. Any attempt to speak to your child in Spanish will, in addition to feeling wholly unnatural, end up in conveying a bad accent and lots of mistakes, to boot. Don't even try. Your job is to pass YOUR mother tongue on to your child, not a tongue that is foreign to you.

But here's what you can do. Tell your little one that YOU want to learn Spanish and invite him to learn it with you. Listen to Spanish songs (and later on, stories) on CD together. Look at photo books with Spanish words in them and try to say them together (ideally, in conjunction with a CD or tape providing the proper pronunciation as a reference). Watch Spanish Sesame Street together. Attend Spanish playgroups together. All of these activities will give you and your child a basic vocabulary. (I should add that you should take this route even if YOU already have this basic vocabulary but do not speak fluently).

Beyond the foregoing, you need outside help. Do you have Spanish speaking neighbours? Employees? A relative? Is there a bilingual or Spanish preschool near you? You will not be able to teach your child a language that you don't speak fluently but you can find the outside resources that will allow your child to learn the language.

Remember, a child needs between 20 and 24 hours a week of a language in order to speak at a "native" level. But even if his exposure doesn't add up to that many hours, your child has a good chance of obtaining fluent comprehension and/or a disposition for the language. And that's good, too!