It got a 37% at rotten tomatoes... not that bad as far as shitty movies go. Compare it with something god awful like Aeon Flux (10%!) and you have a work of art! Seriously though, from the looks of it it looks like about an average Jack Black movie - not great, not terrible, will occasionally make you laugh. Like an amputee.
http://www.rottentomatoes.com/m/nacho_libre/