Sail ships sail fastest with the wind directly at their back, as opposed to tacking across the wind. The fastest way from Portugal to South Africa is to sail roughly south west until a ship hits the equator, and then southeast south of the equator. A Portugueses ship bumped into the Amazon within a couple of decades of Columbus, so assuming Columbus entire convoy is lost at sea, we can have a pretty good date for when, where, and by who would find the New World. Also, the Amazon freshens the sea water up to 45 miles or more from its mouth, and the behavior of birds change near land. These and many other factors let an experience captain of the day often detect land even before land can be seen on the horizon.
The Spanish will be much less important than OTL. The Portuguese may even realize Brazil is no where near China, and may not put a lot of effort into colonizing the new world. A lot depends on how fast the news leaks out of Lisbon, how the Portuguese use the information, and how do other European powers react.