I figured I would at least answer your questions from a teenager's viewpoint (well, at least this teenager's viewpoint).
What are children taught about sex?
Far too little, if you ask me. Most parents don't seem to want to talk about it, most seem to think that kids will learn about it from their friends/media, and that if they don't think about it, their kids won't do it. Bad moves, all of them. As uncomfortable or as funny as it might be to hear your dad try and talk about a penis, you're better hearing it from someone who is experienced than, as you put it, from peers that spread stupid myths and dangerous advice. The whole "Oral sex isn't really sex and it doesn't spread sexually transmitted disease" myth is a great example of this.
Where does information about sexuality come from?
As far as I see it, three main sources. Peers, media, and parents. Friends talk about it a lot, the media talks a LOT about it, although they are sneakier about how they do it, and your parents, if you are lucky, can be a valuable source of information. My own sources are mainly from friends and media, and a bit from talks with my parents, although sometimes I wish that more did.
What are the culture's mores, norms, and taboos?
This is an interesting one. American culture (I cannot say anything about other countries) seems to say that you should hide it until you are 30, never talk about it with anyone, and turn off your libido once you leave the bedroom. Obviously, some of this stuff is unrealistic - kids are not going to stop having sex, and I know from experience I can't just "shut off" my libido once I leave my house. It just doesn't work that way. I suspect the American Culture is raising a group of kids who spend the first 20 years of their life wondering if they are normal for feeling how they feel about issues like sex, until suddenly, they realize that they're actually perfectly normal, and they go on to perpetuate this confusion to their kids by telling them what they were told when they were young.
As far as taboos go, it depends on a lot of things. Age, locale, religion.... In general (note the "general" part), Southern states are more against homosexuality than Northern states. Try and find a chapter on "Sexual Positions" in your high school health book. And heaven forbid you engage in this sex stuff before marriage if you are a Catholic. None of this stuff is going to kill you, but we act like it will. I don't have any idea why we do this. Personally, I don't care if some guy wants to have sex with his boyfriend while a dog humps him, and he watches dominatrix porn on his TV set. As long as he's not imposing that stuff on me, it's fine. And I care a LOT about how we don't teach our kids anything except a plain vanilla "heterosexual missionary position" type of sexual behavior in sex ed classes. As I stated before, when was the last time you heard "Anal Sex" in a high school sex ed discussion. In fact, my high school, to the best of my knowledge, didn't even HAVE a sex ed class, nor does it now. Go figure. BTW, I live in a generally heterosexual Christian middle-class community. What does that tell you about what gets taught and what doesn't?
What are the sources of those mores?
Religion mostly, I suspect. When you ask people why gays are bad, usually their answer is "because the bible says so". Sometimes they say stuff like "because a man and a woman are meant to be together...two guys? It's not natural." So in other words, men are defined as to how macho and manly they are by what goes in their anus. Wierd. I wonder how the multiple figures that show that 30 to 40 percent of men have tried anal sex in some form or another with their wives, and about half of those continue to and enjoy anal sex from their wives, could be used to interpret this...
We seem to have a lot of remenants of a weird Puritan upbringing - I think this has a lot to do with how television commercials and shows can arouse us to no end, but we can't see a single nipple from that hot supermodel. It's all right to tease, but not to actually go through with it - that's not kosher.
How is sexual diversity dealt with?
It's shunned or flaunted, depending on where you live, what religion you are (or the others around you are), and other factors. Some people like to blab on and on about their sexual encounters. Others don't. In religious areas, it's hidden. Isn't it interesting that a lot of bestiality rumors circulate around the stereotyped Bible-Belt farmyard? I guess it's not as easy to supress or deny your sexuality as the religious ones among us believe, and like to tell you. How about all the priests that are dying of AIDS? Guess that abstinence based on faith, in regards to a facet of sexual diversity, isn't as easy as it might seem.
What messages does the media give about sexuality?
That it's ok, it's great, and you're more of a man/woman if you are having sex, lusting over supermodels, and bragging about it. That it's cool to drink and have sex, it's cool to smoke and have sex, hell, that it's cool to do ANYTHING and have sex. That's how advertising works. In this case, it's effective. It preys on something that we all have within us, and uses it quite effective to influence our views about it. The fact that sex is generally a taboo is even more of an edge - remember how great it was when you were young to break taboos just because you could?
What do you think are the advantages and disadvantages of the way the society you live in deals with sexuality and what would you change about the way your culture views sexuality, if you could? ?
I don't see a lot of advantages, to be quite honest. Maybe the scare tactics that society imposes on those who choose to have sex underage helps to prevent unwanted pregnancy and the spread of STDs, but I doubt it. If anything, I think it, like the commercials, helps to amplify it by making it a desireable and forbidden activity.
As for disadvantages, I see plently. Like you, I am disgusted that people hide sexuality like it's dirty or something to be ashamed of. I'm sickened that people try to make sexual diversity something to be ridiculed or denied, because it's doesn't gel with their own morals. And I'm ashamed that we let religion and taboos dictate how our sexual expressions and sexual identities are formed and molded.
Is a society with rampant sex, no taboos, and no religious leashes (in regards to sexuality) a good one? Beats me. But I have to think it's better than one where gays are beaten and humiliated, women are seen as dirty sex objects, and men can figure out how manly they are by not only WHO they have sex with, but also how many times. Stuff like this makes me sad.
"But you [AmberEyes] have never admitted defeat your entire life, so why should you start now. It seems the only perfect human being since Jesus Christ himself is in our presence." -my Uncle Dean