You would travel north to accomplish this trip.
The only ways you can travel along the equator is by going due west or due east and you can do it indefinately. Any other direction you would not be travelling along the equator
you would be in Antarctica.
you would have to travel northwest.
Northwest
SW
Since the earth is a sphere (a ball), you can reach anywhere by going either direction from anywhere. But the trip is usually shorter in one direction than in the other. From the Prime Meridian, the trip to North America or South America is shorter if you head out going toward the west.
You'd be headed nowhere. Since the South Pole is in Antarctica, you wouldn't have to move at all.
South on I-25.
SouthWest
south
The equator is a big place. It's going to be north-ish (that is, the direction should not contain the word "south"), but it could be anywhere from somewhere on the north side of east to somewhere on the north side of west depending on exactly where on the equator you are.
Southwest