In order to fully understand and answer this question, it is important to understand and identify the different forms of conflict presented in the play.  Once you have identified the conflict(s), you can look at the effects of each to see whether conflict is generally presented as a positive or a negative thing.

Conflict means a problem in the story. Romeo and Juliet presents several examples which all revolve around the same two basic problems in the story.

1. The Capulets and Montagues hate each other.
2. Romeo (a Montague) and Juliet (a Capulet) fall in love but must hide their love because of the family feud.

Now, observe the following list of some of the effects of the above conflicts:

1. Street fights which disrupt the peace and call for the threat of harsh punishment for fighting.
2. Neither Romeo nor Juliet have open communication with their parents and look to other adults for advice.
3. Romeo and Juliet both lie to their parents and get married in secret.
4. The deaths of Mercutio and Tybalt.
5. The banishment of Romeo.
6. More lies, a fake death, then the real deaths of Romeo and Juliet (as well as Paris).
7. The families resolve their conflict at the funerals of their children.

When you consider the list of consequences in light of the two basic conflicts in this story, at least six examples portray negative outcomes and only one is positive.  Generally speaking, this presents a strong argument that conflict is presented as negative.