Link: http://www.latimes.com/opinion/op-ed/la-oe-0614-abella-bear-flag-20150614-story.html#page=1
It basically makes out the rebels to be a bunch of racists who rebelled against the nice poor Mexicans and started slaughtering everybody. This seems really black and white, how substantiated are the claims (especially one in particular, it mentions the Californios were planning to secede already and that the Americans came in and crushed democracy or something along those lines)
It should be noted that the rich Californios weren't exactly screwed by the Americans. Most kept their fortunes and some even gained state political office after statehood.
The Native Americans faced extreme hardship during the Gold Rush period. On phone right now, but there is a lot of literature on this that you can find on JSTOR. Their plight has to be one of the saddest things I learned about in college.