Peter:
The previous thread (dated June, 2000) was accurate as of that date. The only thing that has changed since relates to LatinPass, not Mexicana.

Here is a more recent thread if it makes you any happier.
http://www.flyertalk.com/forum/Forum63/HTML/000424.html

But if you don't like the answers you receive here, I suggest you call or e-mail Marriott yourself.