My daughter was really, really into American Girl about 3 years ago. Then, they never had coupons...except for free shipping codes. It may have changed with the downswing in the economy though!
They run a lot of sales on the clothes and accessories - get on the email list. For the actual dolls though, nope. I've never seen a code for anything but free shipping and it's been a long time.
sign up for their catalog. it seems i remember sales and codes for....it must have been shipping. i dunno. we bought my daughter 'marisol' when she was 8. wanted one so bad you'd thought the world was going to end. once she got one (for christmas that year) she never looked at it again. ROFL