First of all, I feel like half the people chiming in here don't know anything about Hopkins and didn't go there. I graduated from undergrad a couple years ago from there, and I'm familiar with the med school as well.
There is no preference for JHU UG, or not a sizeable percentage apply.
Nothing in Hopkins communicates with any other entity, it's the nature of the institution.
That is entirely false. Hopkins med DOES prefer it's undergrads, and I know numerous people who are attending med school there that graduated with me in undergrad. I don't know more than one person attending any other top school from only my year. I don't have an electronic source, but I believe it's on the order of 10x - they take one person from most schools, but take 10 from JHU UG.
Regardless, that should have no effect on your decision to go their for undergrad. As for the "cut-throat competitiveness", that's straight up BS. I was a BME, supposedly one of the most competitive majors around, and I didn't experience it at all. A lot of kids don't go out and study all the time, so sure it's harder to get an A against them if you go out on weekends, but that doesn't make it "cut-throat". I never saw anyone sabotaging anything or other rumors that get passed around.
As for Homewood not speaking to the SOM, they have numerous linkages, so I'm not sure what you're referring to. Many of my friends did research at the SOM, and I personally worked with a couple surgeons at the hospital to create a device on my BME design team, a unique experience that is one of the best parts of JHU. Many of my friends, including myself, hold a patent thanks to that course, not to mention it was a great time.
My only advice to you is to join a fraternity if you're a guy. During the fall of your freshmen year, everyone will go out together and it'll be a lot of fun, but as soon as pledging starts in the spring, the welcoming atmosphere drops off. Starting sophomore year, unless you have close friends in one fraternity, it'll be hard to find a place to go out to. Unfortunately once people join fraternities, they tend to separate from their non-affiliated friends or from their friends that joined other ones. For this reason, joining is critical, IMO. That said, pledging is not absurd like at state schools and there are some fraternities that actually respect their pledges as opposed to making them do excessively ******ed stuff. I never planned to pledge, but I ended up joining one randomly and it was absolutely the best decision I made at Hopkins.
To be honest, I hated it during parts of my sophomore year. The courses were probably the hardest that year, particularly spring, and my fraternity had some issues that didn't give me much of an outlet that year. However, I worked through it, and things improved my junior year and I had the best time of my life during my senior year. The thing about Hopkins is that you have to find your own fun, it won't come to you as easily as some other schools. The administration absolutely SUCKS when it comes to student life, but things are improving. Sure a lot of people are total losers, and a lot of people are ugly, but you'll find a group of people that match you well. Conveniently, the ~500 people that go out tend to not be in that group as much as the people sitting in the library on friday night. I grew a lot as a person at Hopkins and as fun as a school like UVA, with beautiful girls, might have been, I don't regret going there and sticking it out.
Anyway, feel free to PM me if you have any questions about JHU. I'll be honest and without bias, unlike some of the people in this thread.
