Piolín bumper stickers

Just as I thought, those cars we see driving erratically on the roads with the "Piolín" bumper stickers are more likely to be "undocumented" persons (illegal is usually the term for not having documents while residing in a foreign country).

From wikipedia:

In 2005 Sotelo gave undocumented immigrant supporters four hours on his program.[3] His support of the undocumented immigrant protests in 2006 is often credited as the main reason for their enormous turnout, even though many other media personalities helped to make it. He has explained that his own experience of crossing the border illegally and living in the United States as an undocumented immigrant helped him identify with the situation. He is now residing legally in the United States where he encourages peaceful political activism for immigration reform.

In Arizona, this should make spotting illegals rather easy.