I have two responses to a few of the previous posts:
First, in response to the whole topic of "Sal and Holden are alike", because of their mutual avoidance of responsibility, I personally think that that's not true. The difference between the two, it seems to me, is that the continuing refusal to take responsibility in Sal's case is simply because he doesn't want to- there are no particular motivations, he's just a completely empty-minded person who wants to have fun. In Holden's case, though, he does have a mature side, which comes out when he runs out of money, the girls go away and the alcoholic haze wears off; this is when he typically starts to feel very depressed at what he sees as the corruption existant within the world, and starts getting all mopey and gloomy. While Holden uses the immaturity as a shield from his mature adult side, Sal has no mature side, and just lives the traveling irresponsible life without any cares in the world naturally.

Second, in response to Jane's comment about the word "manana". While it could be, as she says, that that the word seems so attractive because of its boundless possibilities, it could also be because it allows Sal, the eternal responsibility-shirker, to put off for tomorrow his adult obligations, saying that there will be more time to complete such tasks as earning money, starting a family or returning home later on.