George tells Lennie to be quiet so the boss will not notice that he is slow.
George and Lennie travel around together, because George looks out for Lennie. George may be smaller, but he is the one with the brains. Lennie is large, and mentally impaired. George looks out for him.
They often get into trouble because of Lennie. The reason they are going to another job is because Lennie tried to touch a lady’s dress. The lady probably was afraid of him, because he is big and was trying to touch her. He just likes soft things. However, they had to go on the run.
Although Lennie is slow, he is a hard worker and a good one. As long as he does what George tells him, he can do his job. George just has to make sure that he hangs on to his work ticket so he won’t lose it.
Now, look- I'll give him the work tickets, but you ain't gonna say a word. You jus' stand there and don't say nothing. If he finds out what a crazy bastard you are, we won't get no job, but if he sees ya work before he hears ya talk, we're set. Ya got that?" (Ch. 1)
When they get there though, things do not really go according to plan. The boss is suspicious because George is talking for Lennie, and he is afraid that George is stealing Lennie’s money. George explains that they are cousins (which they aren’t), and that he is looking out for Lennie, but Lennie is a hard worker. The boss gives in.
The boss turned half away. "Well, God knows he don't need any brains to buck barley bags. But don't you try to put nothing over, Milton. I got my eye on you. (Ch. 2)
George is able to convince the boss that he is all right, but this is just another example of how his going around with Lennie causes trouble. George has to constantly be aware, because he never knows what Lennie might say or how people might perceive them, as in this case. Others, like Slim, are impressed by the fact that George and Lennie travel around together.
The fact that George looks out for Lennie when they are not related is somewhat an anomaly of human nature. He is sometimes harsh with Lennie, such as his reply to the comment about being Lennie's relative. ("If I was a relative of yours I'd shoot myself" (Ch. 2)). However, he is quick thinking, and has a good heart. He protects Lennie, and looks out for him even when he doesn't have to.