I would pick up Latos over Morneau.
as for who to drop, the choices are close.
first thought is Peralta. but he is actually having a good season. the multiple position eligibility on the bench is nice.
Salas is an option, but I don't think I would pick him. he is currently closing for St.Louis. it has been back and forth and sure there's a chance he could lose it again, but there's also the chance that he takes the job and runs with it. if he can get significant saves it would suck to have dropped him.Maybin is an option. hasn't done very well in recent season, but is he now good with SD? the park in SD would work against him. this season he has been better on the road than at home. home- .213/.298/.320/.618/ away- .333/.393/.560/.953/ is it worth keeping him and only using him at home?
what about Sizemore? he has some nice numbers when healthy, but can he stay healthy? currently hurt yet again. hasn't played much in recent seasons.
I might be leaning towards Sizemore. if he's not going to be able to stay healthy, he's not going to be much use. he's only on your bench along with Maybin, so on your team he likely wouldn't see much action. the only thing that would make me want to lean away from Sizemore would be if you could get something good for him in a trade.
hope I helped some.