Just let Mexico have it and get it over with.
@dfwgatorThat is a very good point I had never thought of before. If Mexico were in control of California, there is a very strong chance that they would be much more reasonable than the Californians who are there now.
The Mexican government is as corrupt as all Latin American countries are, but they are not suicidal and they are not loony-toons like the California government is now. Mexico wouldn't let rapist, gang-members, and murderers run free no matter what 'race' they are.
Formally giving California to Mexico is a valid idea that is worth consideration. After all, there is nothing to lose. California has already more or less declared itself as independent of U.S. law. So YES, let Mexico have it. Just one less thing the rest of us have to deal with.