Unfortunately, no luck with 'IgnoreCaptivePortal=true'. The only difference is I now see a certificate error ("certificate is not trusted / the host
www.marriott.com:443 uses an invalid security certificate") but I still can't get through the login screen--it just gets stuck, perhaps due to JavaScript.
I did play around with the terminal in KOReader and ran some wget requests against the Marriott domain but don't see a clear way to actual log in through the command-line.