if you carry on in the game you will face him at least 6 times.
Rival
After you defeat Steven and the Elite Four, you can rebattle your rival as many times as you want.But during the course of the game, you battle May 4 times.4 times and then after you beat Steven AND the Elite Four then you can go to Lilycove City and once a week you can face her again. Hope this helped!
Juan is only in emerald.
in your face it does 10 damage
6 floors. on the first level you face your rival
Stand next to it, face it, then press a
Find your way through Victory Road and you will face your rival at the end of victory road
It's impossible to know what Pokemon he'll have - He'll have a different set everytime you face him.
When you go to Stark Mountain you will meet your rival (you won't battle him/her). After that you will be able to face him at the Fight Area on the weekend(Not on Friday).
after you beat 4 to 5 gym leaders you can face him
You will have to level up a certain type of pokemon like poocheyana for an example...hope it helps!!!!