My friend is having surgery soon...is is appropriate to visit in the hospital?

We were best friends in grade school and into high school. We've both married and have families of our own, so we don't hang out like we used to. We get together once or twice a month to hang out. He's going for surgery soon and will be in for a week or so. Is it ok to visit unannounced? I would go to the waiting room first and see if family is there before entering his room.