This is your yearly reminder to not be an asshole today in the name of racial stereotypes for an excuse to get hammered. You don't need an excuse to get hammered, especially not a racist one. What you can do is educate yourself a little on what Cinco de Mayo is actually about.
It's only really celebrated in Puebla, a state in south-central Mexico. It's to honor the Battle of Puebla in which the Mexican army, against all odds, defeated the invading French army. It's literally to celebrate people of color kicking white dudes out of their country. Don't wear a sombrero.
Now, if you want to do something nice for Mexican people today, you can go to an authentic, family-owned local Mexican restaurant. Not Taco Bell. Not Chipotle. Or, if a Mexican family invites you to a celebratory cookout, you're fine to go to that. Just try not to be racist. For the love of god.
Here's some more information about the Battle of Puebla and Cinco de Mayo. Read up, enjoy, DON'T BE RACIST.