I wrote back on June 15 without a SASE and haven't gotten a reply yet but I sent to Elle the same day and got a signed photo back from her on July 4.

I am waiting to hear back from:

Kay Panabaker
Danielle Panabaker
Aria Wallace
Jenna Boyd
Cayden Boyd
Kyle Chavvirra
Liana Liberato
Dakota Fanning
Elle Fanning
Hannah Robinson