HOW WOULD YOU LIKE SOMEONE to say to you, "Come with me into the bathroom? I want to watch you pee into this paper cup to see if you have been taking drugs." That is what is happening in some shelters for homeless families in Massachusetts. Steve Valero, a lawyer at Greater Boston Legal Services, is indignant about this and has been telling shelters that it is an illegal practice. Some shelter directors claim they had no idea it was illegal. They thought it would be better to have all residents tested for drugs rather than singling out one person.