Just in cased you missed it, here is a very recent NYT article describing the benefits of bilingualism:  http://www.nytimes.com/2012/03/18/opinion/sunday/the-benefits-of-bilingualism.html

We are so fortunate to live in a city where so many different languages are spoken.  What a gift to allow our children to be exposed regularly to other languages by neighbors, friends, and caretakers alike.