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I'm looking for a book from the late 80s. It's about a teenage boy who finds a spaceship out in the country that's crash-landed. There's only one survivor: a boy from a vampiric alien race but he's badly hurt. He's somehow able to show the boy his home planet and the muscular cow-like creatures that his people use for their blood. Eventually the boy's brother, a druggie and Vietnam vet, puts the boy and his alien friend to work making drugs, which they both need masks to do.

Eventually the alien's friends (dressed in skin suits) come to their house. Apparently the boy was a cadet for some kind of interstellar federation, and they want to know what happened. The boy tells them, and an orangutan-like alien (who we are strangely told has the skull of a Hispanic man) and his friends (who are the same species as the boy's friend) ultimately allow him to go with them, as there is nothing for him on Earth after his brother was busted.

The boy is treated more like a talking animal than he is a sapient being because he can't speak the Galactic Lingua Franca, and so when they get to a planet he's taken to be taught and has his brain's plasticity increased so he can learn the language in record time. He's placed in classes with other people from less advanced planets, and he ultimately makes friends with a girl. The girl is an alien from a theocratic planet, and she can unhinge her jaw like a snake's. She eventually freaks out from culture shock, but the boy manages to pass and become a cadet. He also meets a group of humans who were taken from Earth in the 1400s, and who call the alien inhabitants of the planet Devils.

He's eventually given a ship and a partner (whose species looks similar to Big Bird), but they crash-land and his partner is killed by the natives. The boy is imprisoned and tries to communicate with his captives using drawings, but they don't understand him. They're fascinated by his facial hair, as they can't grow any themselves even though they're humanoid, and eventually they allow him to speak to the cameras after he is publicly unveiled. He talks in the Galactic Language and gives them a Reason You Suck speech, but they still don't understand him.

Found it. The book was Becoming Alien by Rebecca Ore.

16-year old boy finds an alien crash-landed on a farm and ends up being recruited to join the Federation of Sapients - and adventuring out among the stars.

First book of a trilogy, although ends in a way that does not require continuation to the other books. Sequels are "Being Human" and "Human to Human". Finalist for the 1989 Philip K. Dick Award. Nominated for the John W. Campbell Award. Nominated for the 1988 Locus Awards.

One of the reviews has a more detailed breakdown than the synopsis and matches my description:

On the first page of Becoming Alien, a teenaged Tom Gentry watches his older brother Warren conduct a drug deal in the backwoods of Virginia. On the second page he rescues a wounded alien from a crashed space probe. From there things move rapidly. He nurses the alien - a sapient, bat-winged marsupial - back to health. His brother agrees that this is all best kept secret since he is operating a drug lab on their family property. The healthy alien, able to communicate through pictures, convinces Tom they should escape together, but Warren figures out what is up and kills the alien in self defense during their atttempt. The Gentry brothers are busted. Warren, now a heavy user of his own goods, gets institutionalized as insane. Tom gets probation. Aliens, poorly disguised as humans, come to investigate the murder. Tom is found innocent and taken off Earth to train as a cadet in The Federation. We have reached the end of the second chapter.

After this things slow down, but not in a bad way. The set up implies that Ore is offering an updated Heinlein juvenile or the opening a grand space opera, but that is not the type of novel she writes. What follows is a thoughtful and imaginative examination of an extreme form of multi-culturalism involving species with evolutionary histories taking them back either to mammals, marsupials, or birds. Earth is not part of The Federation. Human are still judged too xenophobic, nor have we developed the Star Gate technology that allows for FTL travel. Some Tibetans taken off planet 500 years previously have been able to adjust only in the Primitive Zone as free traders.

But Tom is made of different stuff. Although no good in chemistry or biology he is a natural linguist. He settles into the dorm for cadet trainees and learns to navigate the complex politics and power struggles among the different aliens. He also has the usual freshman dorm experiences of arguing over music choices, the tedium of an overloaded schedule, and coping with unfamiliar roommates. One is a bird, the other an ill-tempered furred mammal who comes in only to sleep.

Tom's education involves some dangerous incidents but is built mostly around the complexities of inter-species life and his growing awareness of the tensions that underlie this benign federation. Ore also takes time to describe the group mating rituals of the Gwyngs, the marsupials who are officially Tom's sponsors. He finds he has a somewhat awkward role to play in these. And she explains the workings of the multiple toilet facilities required for a reception hosting a dozen species. I confess that is the sort of thing I often feel is left out of sf novels, and so I appreciate her attention to detail.

Several alien characters are more fully developed than is Tom, but he is narrating the story and he is just a kid from the hills of Virginia. He is chagrined to learn that a descendant of the Tibetan refugees considers him naive. He tries not to be insulted when he must take English diction classes so his accent will not become an intergalactic standard. Those are the sorts of details that kept me involved with a story that is lacking in action. Becoming Alien is also the first of a trilogy, so who knows where Ore will take us next.