Topical for me, I'm on vacation right as I'm writing this!
My favourite vacation spot would probably be downtown Seattle, I've just always really loved the environment and it feels both really comfortable reminding me of home, and like this cool new place I get to explore. Cities on the coast are one of my favourite places to be.
My answer for the last two is the same so I'll say
If I could go anywhere I'd love to visit a good handful of places in Japan that were featured in Love Live. Because that would be my dream vacation. (shocker I know)
But one thing I love about the series is that it just takes place in real places and there so many places I'd love to visit. Examples include Kanda Myojin Shrine, where μ's practiced (which also became a popular spot for people to visit in that show's universe as well), Mito Beach, with the view of Uchiura Bay, which is an incredibly important location throughout Love Live Sunshine, and the Rainbow Bridge in Odaiba which holds a lot of special meaning to me thanks to Nijigasaki and Mirai Harmony. Being able to experience the snow festival in Hokkaido would also be a dream, I see pictures of it a bunch, and would love to visit Sapporo because it's apparently the place Jubilife City is based on.