Some points
The pluses with LA, are that, thanks to hard work in detectives and the exhaustive ground work of Chateau we have gotten footage that we wouldn't get with just random strangers and their camera phones. I can't really stress the amount of time Chateau had to have spent over the last two seasons. I tried it once (missed it by a week, and we should be so glad), because it is truly time consuming and he did it many, many days.
Thats the one plus to LA.
As to the idea of a task before leaving the US, I have to real problem with it with two conditions.
1. No damn starting line elimination, one of the foulest things the production has ever done (that and making teams read hate mail about themselves as a task, this show is supposed to be above that type of behavior).
2. No equalization with flights or once landing in the destination city.
Take season 15, we had a task at the starting line, which determined flights, but the problem with this (besides the stupid elimination) was that in Japan, production equalized everyone (and worse to that, let random chance be what released them, the first and only time that has ever happened for tasks, and it was stupid). But clearly they can let teams arrive and go straight to tasks (they have done that many times).