What is Lady Capulet's opinion of Juliet and Romeo?

It looks like the answer to your question is located in act 3, scene 5.

Here, Lady Capulet completely misunderstands Juliet's grief. It is clear that her distorted perception is occasioned by her lack of discernment. Lady Capulet accuses Juliet of overindulging in her grief for Tybalt. She even suggests that Juliet is not really weeping for her kinsman; she insists that Juliet is sad because Tybalt's killer remains a free man.

Meanwhile, Lady Capulet...

It looks like the answer to your question is located in act 3, scene 5.

Here, Lady Capulet completely misunderstands Juliet's grief. It is clear that her distorted perception is occasioned by her lack of discernment. Lady Capulet accuses Juliet of overindulging in her grief for Tybalt. She even suggests that Juliet is not really weeping for her kinsman; she insists that Juliet is sad because Tybalt's killer remains a free man.

Meanwhile, Lady Capulet thinks of Romeo as a "villain" and a "banished runagate" (vagabond or fugitive). Her desire is that Romeo should die for killing Tybalt. She tells Juliet that she is ready to send one of their servants to Mantua to poison Romeo. 

Privately distressed at this suggestion, Juliet presents an alternative: she will make sure the poison is properly concocted if her mother can find a man to "bear a poison" to Mantua. At this point, we get the idea that Lady Capulet thinks of her daughter in superficial terms. Her lack of discernment causes her to miss the real reason for her daughter's anguish. On a deeper level, Lady Capulet is satisfied with her own interpretation of Juliet's grief and does not feel the need to draw it out.

Because of her lack of discernment and her tendency to railroad her daughter into performing her will, Lady Capulet is unable to fully bond with Juliet. This tragic state of affairs is highlighted when Juliet voices her refusal to marry Paris: Lady Capulet simply becomes furious and takes to wishing that the "fool were married to her grave." Lady Capulet's opinion of Juliet is that she is a spoiled, ungrateful child who refuses to consider her parent's wishes. She does not entertain any other interpretation of her daughter's seemingly baffling behavior.

Meanwhile, Lady Capulet's opinion of Romeo is extremely negative as well. She thinks of Romeo as a killer, who deserves to die for committing murder. Certainly, she does not want to see her daughter marry such a "villain."