What do we learn about Juliet from her speech in Act 2, Scene 2 of Romeo and Juliet?
Although Juliet gives quite a few "speeches" in Act 2, Scene 2 or Romeo and Juliet, I will focus on the scene as a whole so as not to leave anything out. That being said, here is my answer:
The reader learns that Juliet is in love with Romeo (and in love enough to deny her family's age-old feud) and that she is also a bit fickle. Who could deny Juliet's love for Romeo after hearing her "What's in a name?" speech?!?
O Romeo, Romeo! wherefore art thou Romeo? / Deny thy father and refuse thy name! / Or, if thou wild not, be but sworn my love, / And I'll no longer be a Capulet. (2.2.35-38)
Ah, but there is more here than just love. In saying this, Juliet discounts the age-old feud that both families have adhered to for generations. Ironically, by bypassing the guards and eavesdropping by Juliet's private chamber all the while knowing Juliet is indeed a Capulet, proves that Romeo has also discounted this age-old feud. I find it just as interesting that Juliet later addresses Romeo as "fair Montague" (2.2.103), and have always laughed thinking about Tybalt's reaction if he could have been in earshot.
Now I have to enter into a more controversial arena, in that Juliet can also be described as fickle in this scene. Yes, Juliet wants a true declaration of love from Romeo: "If thou dost love, prounouce it faithfully" (2.2.99). However, as soon as Romeo begins his pronouncement as faithfully as he can muster he is met with this statement:
Well, do not swear. Although I joy in thee, / I have no joy of this contract tonight. It is too rash, too unadvised, to sudden; / Too like the lightning. (2.2.123-126)
What!?! She just asked for Romeo to "pronounce it faithfully"!?! Even Romeo gets a bit miffed and says, "O, wilt thou leave me so unsatisfied?" (2.2.132). Ha! Just like a girl, that Juliet.