Yes why is this on a surf blog?
Along all this years doing and guiding tours with a lot of different clients (mainly from the USA). 99% of them get confused is our priority as Mexican certified tour guides to provide the correct information.
5 De Mayo was a Batlle held in Puebla city between Mexico and France (back in 1862) , now days Puebla is 2 hr driving distance from Mexico City.
So why margaritas and tequila are involve on the celebration? I found this link which may clear a little that info:
LORETO Y GUADALUPE FORTRESS
Place where the battle was held still exist very interesting to visit , there is also a museum on site and guided tours inside the tunnels. Place is in high point were you can overlook the vibrant 2 million people city including stunning views to the mountains and one active volcano (Popocatépetl).
Big festivity and Parade still celebrating along one of the main city boulevards called 5 de Mayo.
Please do not get confused, our Indepence celebration is in SEPTEMBER.