No civ has fallen faster than Yamoto in the transisiton from ROR to AOE. Cav rush = Camels which is an ugly bloodbath unless you have a 2 to 1 advantage and even then it will be bloody. As mentioned earlier, if you get Yam in a random civ game, Tool rush and tool rush hard. Later in the game, if its a team affair build lots of high strength boats and help your teammates that way. While most units get wasted by helios pretty bad anyway nothing makes you cry more than watching expensive heavy cav get absolutely rocked by helios.
Lets face the facts, Yam aren't what they used to be and your not going to win many 1 on 1 unit battles in iron with this civ (except naval). Scout rush if you can!!!