Are diamond salespeople trying to take advantage of buyers?
Well, first of all, not every salesperson is going to "take advantage" of you. Of course, they're motivated to do business, but there's nothing nefarious about that. Remember, you're going to be spending money on a diamond no matter what. So you're not deciding WHETHER to spend money - just WHERE.
That said, I'd take a trip down there with no intention to buy. Leave your credit cards at home if it helps! And try to make a few appointments in advance so dealers can properly prepare for you. That way they can put together stones that will be of interest and not just scramble to show you whatever they have on hand.