Are there quotes which portray friendship in Romeo and Juliet?

Various friendships are implied throughout Shakespeare's Romeo and Juliet. Benvolio and Mercutio are friends with Romeo. The Nurse is Juliet's closest friend and confidant and she is also close to Tybalt. Lord Capulet refers to Paris as his friend when he is insisting that Juliet marry the Count. Friar Lawrence could also be considered friends with Romeo and Juliet. 

In Act I, Scene 1, Benvolio, who is also Romeo's cousin, offers friendly advice  about women. Romeo is depressed because Rosaline doesn't love him, so Benvolio tells him to look at other women when they go to Capulet's party. He says,

At this same ancient feast of Capulet’s
Sups the fair Rosaline whom thou so loves,
With all the admirèd beauties of Verona.
Go thither, and with unattainted eye
Compare her face with some that I shall show,
And I will make thee think thy swan a crow.

Mercutio too shows his friendship to Romeo by trying to raise his spirits in Act I, Scene 4. Romeo says he'll just hold the torches and look on at the party. Mercutio, however, has different ideas for his friend. He says,

You are a lover. Borrow Cupid’s wings
And soar with them above a common bound.

The Nurse is not only like a parent figure to Juliet but also a best friend. Juliet relies on her help when she is setting the arrangements to marry Romeo. The Nurse displays her affection toward Juliet in Act I, Scene 3,

Thou wast the prettiest babe that e’er I nursed.

Likewise Juliet shows how close she is to the Nurse when she is anxious to find out Romeo's news in Act II, Scene 5,

I’ faith, I am sorry that thou art not well.
Sweet, sweet, sweet nurse, tell me, what says my
love?

Of course, the Nurse figuratively abandons Juliet later after Romeo has been banished and Juliet's father arranges the marriage with Paris. Juliet will not listen to the Nurse's advice to go through with the marriage to the Count.

The Nurse also refers to her relationship with Tybalt, Juliet's cousin. Apparently, though it is never portrayed in the play, the Nurse and Tybalt were quite close because when Tybalt turns up dead, the Nurse says,

O Tybalt, Tybalt, the best friend I had!
O courteous Tybalt, honest gentleman,
That ever I should live to see thee dead!

At the end of Act III Lord Capulet calls Paris his friend in the middle of his temper tantrum while trying to convince Juliet that she should marry Paris. He says,

Thursday is near. Lay hand on heart; advise.
An you be mine, I’ll give you to my friend.

The most obvious friendship in the story could be Romeo and Juliet, yet it seems as though they are simply lovers. They haven't known each other long enough to become close like friends. Their love is mercurial and short lived. Friendships are usually based on mutual interests and the passage of time. Loyalty, however, is a trait of friendship and Juliet is completely loyal to Romeo, so much so that she agrees to take the potion to fake her death. When the the Friar presents her with the vial, she says, in Act IV, Scene 1,

Give me, give me! O, tell not me of fear!