This song is called Mexican-Jewish Cultural Festival from the episode Picture This and is sung by the Mexican and Jewish people. Here are the Lyrics:

It's a Mexican-Jewish cultural festival!
Mexican-Jewish cultural festival!
Ole!
There is kreplach on tostada,
'Cept for picking a piñata.
We kibitz when we lambada.
How are things in Ensenada?
We put bottles on cabezas
We do mitzvahs up on mesas
And we're coming to your places
With big smiles upon our faces.