Those born deaf often have visualizations of ASL. People who become deaf later in life generally continue to vocalize in their head.
Something I find even more baffling is that everyone is on a spectrum when it comes to visualizing images. A complete lack of visualization is called Aphantasia. On the other end of the spectrum are people with incredibly vivid mental imagery, and everything in between. There's hardly any research on either one of these phenomenons, but I've been seeing articles about them pop up more and more frequently.
It really shows how incredibly resilient and adaptable the human brain is. Most of the people who live with these conditions don't realize they're any different from anyone else. I'm sure there are tons of people who have lived long and fulfilling lives with either one of these conditions.