In Northern Cali there really ain't no beef with the Mexicans out here. We get along with them. Nortenos and Blacks for the most part get along and even have a loose alliance in prison.
Now, in terms of relations with Sur13. That's a different story. Surenos hate the shyt out of black folks. There are more Surenos in so Cal. So that beef has been on for decades. MS13, 18th Street, Florencia 13 etc have all had generations of beef with Bloods & Crips.
But the Blacks vs Mexican beef mainly stems from prison tho.