I think any Dem nominee is going to need a black VP more than a Hispanic one. I don't know why there is all this discussion over the need for a Hispanic VP when the black vote by far is the most important part of the Obama coalition and winning in Nov.
This year is the perfect year to make a major push for increasing Hispanic voter turnout, and many groups, including the Clinton campaign, are already investing heavily in this. In terms of long term success, doing whatever possible to court Hispanic voters now would be in the best interests of the party. Obama already significantly increased African American voter participation for Democrats, so now we need to zero in on Hispanics to open up even more Republican territory.
So with that in mind, I say bring someone like Perez on board as VP to help reach out to Hispanics. If Clinton ends up going against Cruz, this may be more important for the sake of appearances at least.