Jose Acevedo - if he starts 30+ games I think he's got a good shot.
Matt Riley - talented, young...he's got a shot a 150 if he stays healthy...too bad he has to pitch against the Yanks, Red Sox, and BJ's alot.
Oliver Perez - he'll get you 150+ K's, but his whip is horrid (wins won't be too great either)
if the Dodgers call up Edwin Jackson, he could be good. Yates for the Mets has a chance to do well, but I'd monitor his progress for a while. In general, rookie pitchers aren't as productive after the break...something else to keep in mind.
I like Acevedo for some solid numbers, followed by Riley. If you really JUST want to get K's, Oliver Perez is probably your best bet of the bunch.