LP is a very friendly kid. She will wave and say hello to everyone she encounters. One caveat, she won't say hello when I ask her to, e.g., when we are out for a walk and someone waves to her first. Typically she says hello after the person has passed us and is no longer paying attention.
An odd thing about greeting strangers - if I say to LP, "Say Hi, LP" in a sing-songy voice, usually the other person will exactly repeat what I said, including the tone. I feel sort of like a ventriloquist or a hypnotist, getting all of these people to do what I say - even if I am not really trying!
What is great is that just about every time she says hello to someone she leaves them with a smile. You really can't help but feel good when a little munchkin wiggles her little fingers and clearly says one of her only words to you.