Spain is probably infested with these guys, since it has a large undocumented immigrant population. They are mostly laborers from Morocco, but actually, anybody can blend in with them fairly easily.
I was on a train near Valencia last summer when someone who was probably Sudanese got on and took a seat in front of me. He was joined at successive stops by about three other people, one at a time. They appeared to be Arabs, but did not look like farmworkers. (They had the usual overwhelming Arab BO, however.) At first they were very loud and obnoxious, so that all of the Spaniards seated near them got up and sought seats elsewhere. The Sudanese was flailing his arms around, and when his hand grazed me, I too got up to leave.
When I passed them, I realized that a couple of them were speaking to each other - in English. They assumed that I was a Spaniard and didn't speak English because I was reading a Spanish paper, I imagine.
I went further away and sat down; they dropped their voices then, and from what I could hear, it sounded to me as if all of them were speaking English. Heavily accented, but English nonetheless. My only impression was that they were talking about documents, although I assumed this was because Spain was in the midst of one of its many programs for providing documentation to undocumented immigrants.
Since Sept. 11, I have often recalled this scene and wondered about it.