No, you absolutely MUST be a choice rewards member.I should add today I got an Email that said this:
I am pleased to report that the points earned for your stay on June 16, 2012 were sent your Amtrak Rewards account on June 19, 2012; please allow 2 - 4 weeks for Amtrak to receive. You may view your stay activity by accessing your account online at www.choicehotels.com.
So I guess that meant I didn't need to sign up after all?