re: 3 weeks in the USA.

quote:

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This would likely leave a choice between San Diego or another city in the south.

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Then 100% go with San Diego, don't waste too much time in the south. And since you are already going to Los Angeles and San Francisco....will make flights between those areas much cheaper. You can easily get a bus or train between Los Angeles and San Diego.



ETA: Weather in San Diego when you go will still be very nice btw. Can check out Pacific Beach/Mission Beach area, Gaslamp District, Petco Park, La Jolla area, Maritime Museum and USS Midway Museum in San Diego(if you are a history person), San Diego Zoo(one of the best, if not THE best, zoos in the U.S), SeaWorld, Balboa Park, and much, much more.