My dear friend Loren posted this on her wonderful blog: toddlejoy.com. This is very encouraging considering that sometimes I just give up speaking Spanish to the kids just for the convenience of it. I will have to keep up with them and remind them constantly that a dog is a perro!
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.