I say you can drop one of the following: Jesus Montero (you have plenty of guys for the UTIL spot, and you have a great catcher, so once/if he qualifies for C it won't matter), Bryce Harper (he's a FA in my league and a lot of others..it may not be worth holding onto him if he's not guaranteed a call-up any time soon.
Then I would either pick up Billingsley (looked fantastic in first outing, and could be a very solid option this year, especially with the Dodgers playing so well all of a sudden) or Jennings/Infante for UTIL backup/help, as they both provide solid options (I like Jennings better).
Anyone in your league in need of a C, that you could trade Montero to?
I agree that you can let Harper go given that he might not get called up for a while. And even so, yes, he'll be a sexy pick and could make for some trade bait, but will he wind up making your OF that much better than anyone else you've got?
If you're looking to make immediate moves then, sure, add/drop. But you might be able to make room/address your roster through trades if your league is open to it.