Does anyone have any knowledge about the linguistics and foreign languages departments at these schools? I’m trying to decide between them. I will almost certainly want to major in linguistics, a foreign language, anthropology, or possibly astronomy/astrophysics. Specifically in linguistics, I am really interested in endangered language preservation.
Any opinions on choosing between those schools in general would be appreciated as well 
All good schools. Rochester has the strongest linguistics department of the three. Brandies has been rising with a focus on computational linguistics (which is really the application of computer science and statistics to validate linguistic hypotheses).
I would pick the campus you’d want most. I took a look at Mac’s linguistics major, and it will provide plenty to keep you busy. It sounds like you have a variety of interests, so you are going to have a hard enough time fitting them all in regardless – plus you may discover some new interests in college. The good thing about some of your interests, though, is that they likely overlap in terms of meeting major requirements (i.e, you can take a course in one department and it will also count towards a major in another depending on what the specific course is).
While the Mac linguistics major may not offer all aspects of linguistics, you also could take courses in other departments to develop a base of knowledge for other future pathways: such as computational analysis in CS if you wanted to do computational linguistics later on; psychology classes that include information on how the brain processes language, for neurological linguistics, etc.
if you are interested in doing research, either on your own or with a professor, then I would bet that Mac would be as strong as the others. The small LACs are focused solely on undergrad and pride themselves on developing strong student-faculty relationships, as well as nurturing the scholarship of their students.
A Mac education will give you a variety of career directions and practical applications. If you really get the linguistics bug,then most likely grad school would be in your future regardless of which of these schools you attend.
I have to say, I loved Macalester when we visited schools with my kids. The campus itself is small, but really pretty. It’s got immediate access to city life, and the Twin Cities are great! I thought. The students are really engaged intellectually and with their activities.
Brandeis is outside of Boston. If that is a draw, i would be sure to check how often kids actually get into the city. I don’t recall that Waltham itself is that great a place (but I visited a few years ago, so my memory is faulty).
Oops – i overlooked that you are interested in language preservation. While that specific course at Mac is offered only every three years (so you’d have to plan accordingly), the other courses will give you a good foundation for that, and in addition, there are independent projects, etc. where i’m sure you could do research in any topic of interest.
If I were you, I would contact the Linguistics Department directly and ask them about your interests. These colleges want students who will happy and engaged, so they will do your best to answer you honestly.
I also see that they offer psychology of language in the department (to amend my comment above).
What gives Rochester the strongest department? Most well-known professors, most classes available, most people majoring in it?
Most full-time permanent (non-visiting or adjunct), tenure-track professors (not lecturers) who are actual PhD scholars in linguistics who actually do research in linguistics. Many schools have scholars from other disciplines teaching linguistics courses.