URGENT: Please share this with your non-Latino friends before they have a disastrous Cinco de Mayo.
Mexicans and Mexican Americans (and, in desperate times anyone from Central and South America) are a welcome (some would argue necessary) guest/accessory at most Cinco de Mayo festivities. If you manage to cajole a willing Mexican into joining your obnoxious friends as they bellow La Cuacaracha, gargle tequila, wear novelty sombreros, eat microwave taquitos, and try and use their semester of high school Spanish, it can reinforce the air of legitimacy that is a must for such an occasion to go off well. And if that Mexican you bring can be persuaded to smile and tap a Corona bottle against yours periodically or, ideally, tell a cool story about being Mexican, the Mexican (or closest facsimile) will altogether give you the street cred you seek and make your night a culturally relevant one. We think it's tax deductible then. Ask your accountant.
However, please avoid any Mexican with historical knowledge regarding Cinco de Mayo, because you may end up hearing some mind-numbing stories that will dampen your tequila induced buzz. Not to mention that some uppity Mexican will no doubt claim that this celebration of cultural heritage, this acknowledgment of a significant historical event, is nothing more than a beer company's wet dream. But if you read the historical blurb on the Dos Equis coaster at the bar, you can shut that annoying jerk up and then tip your sombrero over your eyes and enjoy a siesta against the bar's inflatable cactus.
Also, try to bring along a Mexican whose pigment is on the darker end of the spectrum (Benito Juarez/Diego Rivera or darker (see Google images, for color palette) since then you will not have to explain that he/she is a genuine Mexican. The last thing you need is a debate to break out while you're trying to school your frat buddy at Golden Tee.
It is strongly recommended that you do not try to proceed with any celebration without a Mexican present.
We wish you a happy and prosperous Cinco de Mayo. May the Corona flow like a rushing river and the bowl of your soul overflow with chicharrones (look it up).
Your handsome and humble servant,