These drummers were part of the Mexican Army's annual parade on Dia de la Independencia (the Mexican Independence Day). It takes place on 16 September, starting at the Mexico City Zocalo and marching down Paseo de la Reforma.
It's a huge parade, seemingly involving the entire army. I stumbled across this as I was making my way to the Zocalo to check out the preparations for a large protest in support of Sr Lopez Obrador.
Posted by Jack on 16 September, 2006