L,L,R,R,square, circle,x, triangle
I have not finished this game yet, but I'm pretty far, and so far, the best training area I've found is at the very beginning of the game, outside the first town when you still have Lance, Knight and Soldier in your party.
Since all the characters leave your party due to circumstances right after the first town, there is no need to train them, so Have them killed in battle, and because all the enemies are EXTREMELY pathetic, Lloyd is able to pick them off like nothing. But remember, every battle, the dead become revived with 1 HP, so just have those character get hit once, and Lloyd kill off who ever is still remaining at the very end.
I got Lloyd to level 20 within an hour and a half, and Still, have not needed to train him ever since (he gains few levels from other battles).
Nor have I needed to train my other characters because Lloyd still dominates. Hope all you people just starting to play the game enjoy this tip.
This will only work if your characters are not yet equipped with armour. This is very simple, all you need to do is buy just one armour for the character you want this to work for and make sure he has no other armour equipped. Once you have bought the armour of your choice save your game, then equip the armour and then load your game. You will notice that your characters defence stays the same as if he has still got the armour equipped but he has not, then simply repeat the process and there you have it, infinite defence increase.
In Weststone Village, go to the old peoples' home, and on the left side of the middle table, go to the bottom of the left side, and press right on the d-pad. The game the shakes fast, almost impossible to see, and Lloyds skin colour changes from white, to black.