I'm currently doing my senior year abroad in Germany. If you want, you can ask me, or anybody who has previously done an exchange, because we probably contain the best advice.
Also: Try to go to a country that you have language experience in, or get some experience before going in, it will really help.
I've heard amazing things about Brazil, everyone that is an exchange student in Hessen (The state I'm living in) is like, holy fuck this is amazing!! Love every minute, while brazilians are like "meh" and I've heard of Brazilians wishing they could go to Brazil haha.
Anyhow like someone said before, any country, any culture is an experience, if you can do it, do it. I personally like Europe, had German experience, and like the culture came here. Not the super party life, but drunk pretty often and out on the weekends, besides that school really is big part of the week, its not like people are going out after school all day, average day is going home after school, relaxing, studying.
Overall I'm enjoying my year so far, and would recommend an exchange in its entirety, and that Germany is a great place to go as well.