O yes he's riding.
He's in the team Astana and is theoretically there to support the team leader Alberto Contador, who is also favorite to win.
Astana have another American Levi Leipheimer who is also very good. The team is so loaded with talent they will either be the best team or the will implode under the internal rivalry.
Could LA win it? You never know, he has a wealth of experience, he's as cunning as a fox, but he is getting on a bit. He has himself raised the Michael Jordan issue. Armstrong won't disgrace himself, he is in very good shape.