McALLEN, Texas - In McAllen - where families go back and forth across the Mexican border for dentist appointments and soccer games - Spanish and English co-exist on billboards, in classrooms and on the radio.
Now, McAllen's bilingualism is being taken to a new level: Deaf students in the school system are learning Mexican Sign Language.
Which is not to be confused with Spanish Sign Language. Or any other sign language, for that matter. Sign languages differ vastly from country to country, even when the countries have the same spoken language.
It is highly unusual for U.S. schools even in border areas to teach Mexican Sign Language. And the class in McAllen is nothing short of a revelation for the 10 deaf students taking it.
Take Margarita Schulse, a 15-year-old who crosses the Rio Grande every weekend to visit Mexican relatives. After church, Schulse settles in with her deaf 18-year-old cousin.
The problem is that the Mexican cousin knows only Mexican sign. And until this year, Margarita knew only American sign. The teen-agers struggled to communicate through crude pantomimes but never got far.
''We do our best, but it's very hard,'' Margarita explained through an interpreter. ''Her sign language is totally different from ours.''
''They cross the border and start signing, and nobody understands a single word they're saying,'' Mexican Sign Language teacher Jennifer Powell said. ''They're lost over there.''
Not even Gallaudet University in Washington, the world's only university for the deaf, offers courses in foreign sign. ''I've never heard of such a program,'' said Shirin Antia, a deaf-education professor at the University of Arizona.
Every nation has its own sign language. Deaf Americans who wish to chat with their British counterparts are out of luck: The two alphabets have almost nothing in common.
If you didn't know any of this, you're not alone.
''Everybody just assumes sign language is universal,'' said Clara Cardenas, a McAllen counselor for deaf students. ''But the languages from each country are totally, totally different.''
That difference can mean a lot: In American Sign Language, two hands cupped at mid-torso means ''complain.'' In Mexican, the same gesture means ''excrement.''
Mexican Sign Language employs a more complex system of signs. In the United States, there is no difference between, say, ''easy'' and ''easily.'' In Mexico, adverbs are illustrated in two or three movements, their suffixes spelled out.
Bilingual sign classes are unlikely to spread very far in the United States, said Maria Flores of the Austin-based Texas School for the Deaf. Most immigrants are quick to drop foreign sign languages, she said.
But in McAllen, ''we all just sort of thought it made sense,'' said Dan Diffee, director of the program.