Good point spoiler.
OG
Thanks
But what do I do if I start a game, my heart set on playing the Ruy, and play e4, only to have my friend suddenly play c5??? He wants to play the Sicilian and I don't know how.
It's a good question, and there's probably many valid answers. For me, i'd treat it like I would if we were in some middlegame position, and evaluate the position, and try to follow good opening principles and develop the best I could.
Working out what all the things your opponent's last move did for him, and calculating any checks, captures, and threats each of your candidates would suffer seems like a nice start.
If you are up for learning a new system, the closed sicilian and c3 sicilians have fairly good reputations.
http://chesslessons.wordpress.com/category/morra-gambit/
GM guy teaches how to defend against sicilian
The King Indian attack is a good line against the sicilian, french or caro cann if u want to stay away from main lines.