In what "language" do people who were born deaf think in? (i.e. I have to remember to buy eggs.)

we know words, we use pictures too.

A friend had a son who was not diagnosed as being deaf until he was 5 years old. The mother discovered one day that he had learned how to read lips. The thinking up till this point was that he was autistic. He grew up to be a normal kid, thinking in English even though he never heard the sounds.

Very interesting. Maybe they think through imagining actions, movements and gestures.

They would think in pictures and images. A lot of use without a hearing loss think this way.

They do not "think" in the way you're asking. To have thoughts in words, one must know words. The thought process is otherwise incomplete. They can only relate through feelings and perceptions, so until they learn a language with words, the thought process remains broken. They would not think "I need to get eggs", but like any person without language, like a feral child, they may see food and associate it with a way to assuage their hunger.
Does that make sense?

i'm not sure but interesting question...

Seems it would be the language they use to communciate with through sign language or lip reading.

...they think in sentences i guess lol +2

that's a really good question and I have no idea. +2 not sure why you're negative!

IT is an interesting thought. When you consider that someone who is born deaf cannot and has not heard any sound of language and the only language they have is with their hands or written, then you have to consider they do not have a "voice" inside their head.

But to have that voice in our head seems to be almost intrinsically human. Surely we ALL think to ourselves, so what would one say to one's self with no language to say it with? Maybe it's symbolic association, mental imagery or their own language that makes sense to them?

I think it would be images and emotions (hunger, having cravings for omellette...etc. in case of eggs)