If not LA, then the next destination to look at would be San Diego.
Since we haven't had any sightings aside from the ones at LAX for the final leg, I have to assume they held the detours and roadblocks for the final leg away from the eyes of the public. This suggests to me that it didn't happen in a large city or if it did, all tasks were done indoors where there would be little visual evidence to the public. The trend has been this way the last couple of seasons.
Last season in the final leg in San Francisco, we knew about the Letterman Digital Arts Center and Coit Tower. Those were reasonably public and word got out. We also heard about The Great American Music Hall, which I think was lucky on our part because there was little to see on the outside of the building to suggest anything was happening there. I assume we heard about that because some team must have been asking people for directions to it. We heard nothing about Candlestick Park aside from a rumor about Hunter's Point, which is not surprising because Candlestick Park is a very isolated location with no one around unless an event is happening there.
This season, they started in an unlikely location at Gloucester, MA and we could easily have missed it if the guy working at the marina hadn't had a camera. I'm guessing that the final leg will be at an equally unlikely location. I'll do some real speculating here. I lean towards a remote isolated location, possibly in the desert, perhaps one of the Channel Islands off the coast from Los Angeles (not Catalina - too many people around). Camp Pendleton or one of the military bases in the desert is possible, but I think too many soldiers would know and word would get out. Also, since they had soldiers on the previous leg in South Korea, I doubt they would do it again on the next leg. There are also places in the mountains around Los Angeles or in the Southern Sierras that might work as well, but I don't know them well enough to suggest any good locations. I'll throw my vote to some cool location like the ghost town at Bodie or Mono Lake
or even Death Valley
. Scratch Death Valley. It was probably over 115 F (46 C) that time of year.
Actually, I'd really like to see Area 51 in Nevada. They could have Phil and a Grey Alien at the finish line.