Just last week the Federal Police (similar to the FBI) disarmed the local Tijuana police because corruption and bribes from drug dealers have reached all government institutions. During Fox administration (2000-2006) 9,000 people were murdered in drug related executions. This is a higher per day average than U.S. soldiers killed in Iraq.
Wealthy businessmen, politicians and maybe even some drug dealers are sending their families to the U.S. for safety. Chula Vista for them is a paradise compared to Tijuana. Not all of them will relocate to Chula Vista, some can afford places like La Jolla. Most of these people will have legal or semi-legal status (tourist visa). I see this as a phenomenon that will be on the increase, rich people from Latin America fleeing to the U.S. as crime in their countries escalates. Lax immigration laws make this very easy for wealthy people. The free market economy that started with NAFTA has created a huge wealth for some people in Mexico (Carlos Slim, the third richest person in the world is Mexican). Assertive macroeconomic policies have also created a strong Peso and a low risk level for investing in the country. But even though Mexico is now a safe and profitable place to invest your money (the Mexican stock market has done terrific in the last years), crime is rampant in most of the country and it is not a safe place to live.