Recommended translations:

• Plato: "Protagoras" and "Meno", trans. Robert C. Bartlett (Cornell, 2004).
• "Protagoras," trans. S. Lombardo and K. Bell in Plato: Complete Works, ed. J. M. Cooper (Hackett, 1997).

Excerpt:

Friend
Where have you been now, Socrates? Ah, but of course you have been in chase of Alcibiades and his youthful beauty! Well, only the other day, as I looked at him, I thought him still handsome as a man—for a man he is, Socrates, between you and me, and with quite a growth of beard.

Socrates
And what of that? Do you mean to say you do not approve of Homer, who said that youth has highest grace in him whose beard is appearing, as now in the case of Alcibiades?

Friend
Then how is the affair at present? Have you been with him just now? And how is the young man treating you?

Socrates
Quite well, I considered, and especially so today: for he spoke a good deal on my side, supporting me in a discussion—in fact I have only just left him. However, there is a strange thing I have to tell you: although he was present, I not merely paid him no attention, but at times forgot him altogether.

Online:
Amazon (Recommended Translation: Bartlett)
Amazon (Recommended Translation: Lombardo and Bell)
Project Perseus (English, Free Access)
Project Perseus (Greek, Free Access)
Project Gutenberg (Free Access)