Are there any good mothers in the Capulet family?

Not really, no.  Lady Capulet is not what I would call a good mother.  She is eager to force her daughter, Juliet, to marry at thirteen years old and to become a mother, despite the fact that this is what she did and her own marriage seems to have its issues.  This makes her seem more concerned about what is socially appropriate or proper than what is best for her own child.  Later, when Juliet...

Not really, no.  Lady Capulet is not what I would call a good mother.  She is eager to force her daughter, Juliet, to marry at thirteen years old and to become a mother, despite the fact that this is what she did and her own marriage seems to have its issues.  This makes her seem more concerned about what is socially appropriate or proper than what is best for her own child.  Later, when Juliet refuses to marry Count Paris, Lady Capulet basically abandons her to Lord Capulet's wrath, saying, "I would the fool were married to her grave."  Basically, then, she says that she wishes Juliet were dead rather than disobedient and ungrateful. 

The nurse, I would argue, is a better mother figure than Lady Capulet is.  She seems to genuinely care about Juliet in a way that her own mother does not.  However, she does give Juliet bad advice, and helping Juliet to form a relationship with a forbidden young man -- especially when she knows that her parents are arranging another match -- is a serious error in judgment.