Yes you can and I can tell you from personal experience it's not easy and they are mean as heck. but yes it is possible to hitch a ride. There is even some place that holds races with jokeys and everything.
Roy : I guess me and you can have a rodeo now LOL, I still have lumps from when I tried to ride one. I have a friend who had 200 of them back when all the knuckleheads thought they could get rich quick and the then the bottom fell out and they took a $$ bath.
But they are mean suckers, and can kick like a mule.
An emu is not sturdy enough to carry weight, they only weight 125 lbs - 150lbs vs the 500 lb ostrich, which are more commonly ridden. Mine are hand raised and are very docile animals. They will also lay down if you put weight on them.