Is CAHSU in a safe area (by safe, I mean could I walk around early evening without getting mugged etc)

Yea, it's pretty safe.
Most students live in Los Lagos. It takes about 5 minutes to go to school by a car. If you walk, it takes 20-30 minutes, but there are no sidewalks. So, it's kinda hard to walk. Especially at night, it's too dark and people drive pretty fast. I never heard people getting mugged while they walk from the school to Los Lagos. In fact, nobody really walks. They all take the school bus.
I would definitely NOT recommend walking around in the city at night or taking a cab from the city by yourself. Always stay in a group if you go out.