I would, because:
1. The VP is less a factor - the Prez calls the shots, and I believe Cruz would call Walker out when necessary.
2. I don't hate Walker, but I believe, based on his own words and actions, that he's far less a Conservative than Cruz, and too close to a RINO for my tastes
3. Given the VP slot, Walker could change my mind, but I would rather see him in action in a spot he can't screw up too bad (if Joe Biteme can do it, anyone can), and one that would give him more of a chance to prove his real Conservative chops. If Walker gets the main spot, I believe he'll govern a lot like Bush, and lets face it, Bush was a disaster to the Conservative movement.
Would you vote for Cruz if Walker was on the ticket as VP?
I would, because:
That means you would compromise your principals no matter how much you try to rationalize it.