To understand this film, it's also key to grasp the how Chileans are an extremely classist society, with well-defined socio-economic strata. The economic and social elements of each class have been and are clearly distinctive. Anything not within the accepted boundaries of that class is considered "alternative", "offensive", "wrong", etc. For Chilean upper (and generally ultra conservative) class, such issues are homosexuality, drug use, non-traditional career choices and these are the exact themes of "La Sagrada Familia".
The film follows a traditional Chilean couple and their son who decide to spend (as many people in the country do) their Easter weekend at their beach house, where they will finally meet their son's girlfriend: an oversexual drama student who does drugs galore, is anti-Catholic and who will wreak all kinds of havoc with those who meet her. The weekend will also be an opportunity for the son to create new and stronger bonds; especially touching is the relationship with his sweet, non-speaking neighbor, who secretly loves him.
Although the issues might have been dealt with many times before in film, it is because they are so unspoken of and repressed in Chile and because of the actors' ability to portray that internal turmoil with such brilliance that the film shines. Each conversation, each revelation, each glance, feels raw and genuine; in fact, when the film abandons this and becomes overphilosophical in its approach is when it fails and drags. Fortuntately, those moments are few and far between and the end result is a satisfying one. The final act is refreshing and honest, and absolutely consistent with the the characters and the story. I totally recommend it.
