Hi Ashley, Thats a great question!
I'm a Public Health major and I'm also minoring in Econ and English, so I think I can answer this one. Hopkins definitely does have a fairly large Public Health program, but they have changed it since I declared my major, so it might be changing a little in size now (it will no longer have two "tracks" to specialize in).
As a PH major you do have to take a few core classes: Epidemiology, Health Policy & Management, Environment and Your Health, and I think three others that I can't think of right now. Those six classes are definitely not small, but they all do break down into 20 person sections and you can get to know your professor really well if that's what you want.
They are pretty big classes, but those are only six out of your whole major--everything else is in your hands. You have two concentrations within a social sciences focus, so I chose History and Poli Sci as my concentrations--these classes, which take up a lot more of my time at Hopkins, are much smaller. I've taken Global Public Health Since 1945, Chinese Cultural Revolution, and a bunch of others for those concentrations, and you can pick and choose these classes to suit your own preferences. I know some people who love big lectures, and they've been able to find classes that suit them, while one of my roommates refuses to take a big class (she's also a public health major) and she's managed to fill three years with classes where she knows the professor well. It really is totally up to you.
The great thing about Public Health being such a big program at Hopkins is the resources you get as a result. Public health advising is incredible, the study abroad office knows your major requirements, the career center has tons of jobs for you, and then you have research opportunities everywhere you look because of the Bloomberg School of Public Health, as well. It really is a great subject to study, and Hopkins is one of the few universities where you can pursue Public Health as an undergrad. Don't let the fact that you might have to take a few big lectures turn you off, you might find you really love them!
Hope this helps, let me know if you have any other questions!