The best place to do it is at the Battle Avenue, around that small fountain in front of the Masalada (I never knew how to spell it) shop, on a Tauros. It is a repeating, circular path that is small, and no one will disturb you while you are egg-hatching. Also, if you have a Pokemon with Flame Body or Magma Armor, the egg will hatch faster. You can also leave the egg at the hot spring part of Poke Pelago.