The informant learned this joke, which falls under the category of blason populaire, from one of his friends in junior high school. He says that he has also heard it from other active bearers as a black joke:
How do you stop a Mexican from drowning? The answer is, of course, take your foot off his head.
The informant says that when he performs this joke it is usually in a group of friends who consider vulgar jokes acceptable and that he varies the ethnicity to match the groups prejudices. He also admits that sometimes he tells the joke when hes around people who are racist and he doesnt want to make any waves.
He considers it to be a pretty bad joke but says its easy to use for a cheap laugh, as an icebreaker.
The informant grew up in Tujunga, which according to the LA Timess 2009 Mapping LA project has a black population of only 1.8%. It is therefore not surprising that he would have heard the “black joke” cognate, since the members of the audience to the joke would have been unlikely to be black or have black acquaintances on whose behalf to be offended. However, it is perhaps more surprising that his friend told it to him as a Mexican joke, since according to the same project, 14.7% of Tujungas residents have Mexican ancestry. It may be that the joke was more acceptable to tell because some members of the active bearers audience had Mexican ancestry and were willing to laugh at themselves, or perhaps the informants friend had Mexican ancestry himself.
Source: Ardalani, Sarah, et al. Tujunga. Los Angeles Times. 2009. Tribune Newspaper. 25 April 2011 <http://projects.latimes.com/mapping-la/neighborhoods/neighborhood/tujunga/#ethnicity>.