Rubio would be a disaster. He has already indicated a desire to continue the flood of illegals, although he claims to have changed his mind. I don't trust him.
Cruz is my first choice. He is the most solidly conservative of the bunch. I might consider Walker as a second choice if he runs, but only if he clarifies his position on immigration. I've heard and read so many conflicting stories, I don't know what to believe.
http://www.freerepublic.com/focus/f-news/3294905/posts
I think Walker is heads and shoulders ahead of all the candidates when it comes to immigration. Even Cruz who is my second choice is not doing great on immigration according to the link.
I don't think Jeb really wants to be President. I think he's running only because he believes this is a natural career progression for him but I get the feeling his heart's just not in it.