There's plenty of time. Go south from the memory start, sprinting straight to the exit. Grab the horse immediately to the left of the exit. Check the map, and head to the nearest checkpoint. When you get close, leap off the horse, and sprint to the target, tapping Y as you get close. Rinse and repeat, you should have at least 20 seconds left when you get to the third target.
Yoda of Borg are we: Futile is resistance. Assimilate you, we will.
No its not the same thats the problem, This is a PS3 Version and not a X-BOX 360 Y may be in the same spot as Triangle but this is a PS3 Assassins creed Board. So unless you have both why are you on a PS3 board?