I chose Chile because I wanted to discover and ultimately fall in love with a country I knew nothing about prior to my choosing to live and study there. The USAC Santiago program had all of the program aspects I was looking for: the ability to have all my classes in Spanish, the accessibility to traveling advice (and friends to travel with), and the option to live with a host family. I loved my professors (especially Señor Julián Gutiérrez); they made Spanish fun and surprisingly easier to learn. I loved my program director and advisors; they were so easy to talk to and always were down to talk and have fun. The friends I made are all super unique and amazing in their own ways (both local university students and the students sharing my foreign exchange experience in Santiago). But my host family was the best aspect of it all; they taught me to cook, corrected my Spanish, and accepted me as their own. That was definitely the best part of the entire thing - knowing that, even in a foreign country with zero familiarity, there is a family for you that accepts you and that you could always turn to.
As for some advice: definitely opt for a host family for the ultimate integration experience. Apartments are cool, and you definitely have some more freedom, but when it comes to living in your typical Santiago barrio with a cool family that cooks and cleans for you as well as gives you unlimited advice and guidance, you really can't go wrong. Practice your Spanish as much as you can, even if you're embarrassed! People will always appreciate your effort and you will definitely learn more than you ever thought possible. Finally, don't be afraid to travel! Chile is the most amazing place and country ever, and South America is an entirely different world (geographically, at least). Take advantage of your time in a big city, but also don't forget that the Andes and Torres del Paine are waiting for you!