What the top comment doesn't mention is that there were plenty of Jews, Christians, and apparently "Sa'bi'" in the area of Arabia as well. Indeed, there were several Jewish tribes which Muhammad famous allied with and fought against. For more on Sabians, see here. However, my impression is that while these groups were all present around Medina, we have a no direct historical or archeological evidence that they were specifically around Mecca (there were Jews and Christians other places in Arabia, like Yemen). Muhammad himself was described as a hanif, but we really don't know very much what that means besides sort of an independent monotheist. It's unclear what, if anything, the term meant before Mohammed's time.

It's controversial to say how much these groups affected Islam. The secular Western consensus seems to be Donner's position, that early Muslims saw themselves in alliance with regional Jewish (and to a possibly lesser extent probably heterodox Christian) groups. /u/shlin28 goes into detail about the relationships between early Muslims and Arabian Jews and Christians here and here.