I got the same pin code in the mail too. I don't believe the offer is transferrable, as it is tied to your name and address.
My offer came addressed to my maiden name and I had trouble calling and asking for a rate based on the code. They said it wasn't me (I've made several reservations in my married name) and wasn't linked to my account so I couldn't use it.
This is the second pin code offer I've received and the second time I've had issues trying to use it. Both times, they got kind of mean too, like I was trying to pull one over on them.