Publishers are traditionally awful when it comes to sending along author mail, sending it without first opening it, sending it in a timely manner, and sending it with return address intact. One is usually about as bad as another in my experience--but, since I'm currently doing a lot of business with them, you may as well send me mail in care of:
Please Forward to Author
Simon and Schuster, Children's Books
1230 Avenue of the Americas
New York, NY 10020
Once I get mail, I try to answer it promptly--but there are times when I get swamped, and things lag. Best way to get a fast answer is right here--this forum. (You can also request that our friend Evan forward it without posting, if you so desire).