Puerto Rican Hispanics have a right to be here, they are US citizens. The Hispanic influx seen in the Elmhurst area were not Puerto Ricans or Mexicans for that matter but people from South America..some legal and many not.
Mexicans have always been part of lower California since it originally was part of Mexico until the mid 1800's. What has happened is people are migrating through Mexico from Central America and beyond. Speaking the same language and having a similar appearance, not too difficult and until recently, Mexico not doing too much about it, closing their eyes as long as they kept moving to the US.