Its a good trade if you think that Cruz will stay healthy. I never invest too much into Cruz for that very reason. While you can't predict injuries, some guys just have a habit of never playing a whole season. Cruz is certainly an extreme case of that.
Personally, I think you could be more Stable with Choo, and find another deal or someone on the WW that could make up the difference between Martins' stats and Sotos' stats.
Absolutely go for this trade. Yes, Choo is going to give you good numbers across the board in all categories, but Cruz has the potential to lead the league in RBI, in my opinion at least. Take Cruz's numbers in 2010, an adjust them for a 150 game season, here are his numbers. 108 RBI, 30 HR, 23 SB, 83 R. Now those aren't unheard of numbers, but considering that he was battling lingering injuries all season, I would bet those numbers are higher. I would jump all over this.