When you click on the sign up link, you are taken to a page on the HHonors website that asks for you to choose between Double Your Points and Double Your Miles. Me, being an AGR member, selected Double Your Points because Amtrak doesn't go by miles, they go by points. Unfortunately, the teeny fine print below those options clarify (vaguely) that the points are for HHonors and the Miles are for AGR points (or other airline miles).
Starting April 1, sign up for the Double Your HHonors promotion and you can earn Double Amtrak Guest Rewards points when you book and stay at any participating hotel or resort within the Hilton Worldwide portfolio by June 30, 2012.
Edited by VentureForth, 27 June 2012 - 04:08 PM.