It's in the yard of a house my friend is buying. It was growing either on a tree or a very tall bush.
EDIT: They're definitely not a hibiscus. Too many petals and the stamen/pistil is different.
EDIT2: Maybe they are hibiscus. I've just never seen one that looked like that before. Hmm.
EDIT3: manpaya figured it out! Camellia!! Thanks!