How do I unlock my Mac without having to click my name? In Snow Leopard, at least, I could press Cmd + L to select my name and then press Enter to get the password prompt, but I can't get that to work in Mountain Lion when I've left the computer locked for an extended amount of time.

How do I unlock my Mac without having to click my name when I've locked it?
Just by typing the first letters of the user's name should select that user. Afterwards, as you say, pressing Enter will prompt for the password.