SUDDENLY sign language is everywhere, on TV, on Broadway, in the classroom, at the art museum. It's as great and as happy a change as the coming of spring. After generations of scorn and shame and hiding, signing is out in the open at last, where hearing people can see it, and where those deaf people who depend on it can be proud of it. And just as suddenly, everyone wants to learn it. More people are signing or studying sign today than ever in history. And it bodes well for the place of deaf people in society that many of those it has captivated are very young.

Kids have a special, happy affinity for signing. They're energetic, unpretentious, imaginative natural mimics, just like any skillful singer. They relish the idea of learning a "secret" code. They're open to people unlike themselves. And they have a propensity for language learning generally that is the envy and despair of any adult language student. In short, they're perfect candidates for manual communication. The only question is how to teach them.

The authors of A Show of Hands believe that a first exposure to sign ought to come as part of a larger introduction to deafness and deaf people. This is a very sound idea, because a child's attitude toward signing is more important, and more lasting, that the smattering of signs he'll pick up from a book. (Truth be told, it probably isn't possible to learn sign language mainly from a book. It's unwritten, totally visual, and based on space and movement, all the features of experience that still pictures and words cannot convey.) Sullivan and Bourke disguise a quite surprising amount of solid information as a stylish picture book, and pitch it to the preteen sense of humor. Any reader of Mad magazine will chuckle consistently through A Show of Hands.

It's a cheery, earnest, well-meaning, but, unfortunately, a muddled effort. The ideas develop nicely and the jokes come at least once a page. The illustrations are droll and observant. But the breezy sarcasm, obviously intended to win a child's interest to this very serious subject, almost torpedoes the whole enterprise. The authors haven't decided whether they want to be funny or wholly factual, and it's a shame, because they have some worthwhile things to say. But throughout the book signs are presented for example in humorously appropriate circumstances. George Washington demonstrates "first," Mona Lisa shows us "smile." The trouble is that presenting certain signs accurately in two dimensions can tax the most careful technical illustrator. No one I asked, for example, could get "name" right from the picture in the book. The illustrator, Bourke, had paid more attention to characterizing Rumpelstiltskin (a witty touch, to be sure) than to getting the hands properly oriented to one another.

Sometimes the tongue-in-cheek tone even keeps us from understanding what the authors really mean. They title one chapter "Signing Is a Cinch," a statement that is true only if meant ironically. A mild blowhard named Sam lets it be known to his friend j.B. that "of course, signing was a cinch for me right from the start." Are we meant to take him literally, in wich case he's also a fibber, or to discount what he says in light of what we know of him? Elsewhere we learn that "fingerspelling is so easy you can spell 'encyclopedia' with one hand tied behind your back." It's true, of course, that fingerspelling takes only one hand, but it's not really fair to imply that doing it decently is anything close to easy.

Sesame Street Sign Language Fun is more modest in its goals. An outgrowth of the TV who, it features Linda Bove, the deaf actress who is one of the regulars, demonstrating a variety of signs in clear, if sometimes undersized, color photographs. Care has been taken to make the signs as understandable as possible. Unlike Bourke's creations, Bove wears an unadorned solid-color sweater, just as professional interpreters do, to insure that her clothes won't compete visually with her hands.

The book has no story line and presents essentially no information beyond the signs, which are arranged in simple sentences or grouped in categories like "feelings," "opposites," and "people in the neighborhood." For the child (or adult) who simply wants to learn some signs, this workmanlike job may well be more useful than Sullivan and Bourke's far more imaginative effort, although the Sesame Street format might put off some grade-school sophisticates.