So many questions about so many Cruzes
Juan's situation is actually very similar to Jose's in that the next three or four weeks could be decisive for their seasons...
I think Jones and Jose Cruz will post very similar numbers in the short run. While it may sound strange, I think Jones has a slightly higher upside than Cruz at this point. The trouble is that the risk that comes with him is much, much greater: if Jones doesn't start hitting lefties pretty soon, he'll be seeing a lot of bench time (or worse, pinch-hitting duty where a single at bat costs you a game off your limit). Strikeout totals should be similar for both.
On the whole, the more important either player will be, the better Cruz looks. If either one would start or be your first of off the bench, go with Cruz. If you have a very deep bench and several solid of's already, taking a gamble on Jones might be the way to go.