First, quit dealing with breeders on the internet unless you first meet them in person.
Second, really look at some things before you even consider the breed, such as: check your homeowners insurance (or your landlord's insurance) to be sure it doesn't list certain breeds.
Consider where you live in Los Angeles. Enormous, crowded area. Do you have enough space? What are your neighbors like (they can be SUCH an issue if they see a "pit bull")? If you have any adjoining yards with any kind of dog, is your fence absolutely jump-proof and tear-apart proof? Is there any breed-specific legislation in your area?
You should be able to find a UKC or ADBA show in your area (look on their websites for show schedules). GO SEE and talk with the owners whose dogs you like. Try to get a relationship going and go see their place (I don't like dealing with people whose dogs live in crates and this does happen). See what their dogs are generally like.
I think you do understand that especially other dog aggression can be an issue. But I have known several who, when raised on a farm from a young age and exposed to all kinds of stock, do just fine. It MIGHT be easier finding what you want with an Am Staf, but again, ya kinda got to know the breeder and the kind of dogs he raises.
