I've hijacked many vacations to write. Mostly because writing has become such a huge part of my daily routine, Like brushing my teeth, it just feels icky when I don't do it.
A lot of writers say they can only write under certain circumstances: a certain room, noise level, lighting, when all your books are stacked just so or the M&Ms are sorted into bowls by color. And I get it. It's not easy to write just anywhere. But it's important that you try to block all that out and try.
Don't force it. The last thing anyone wants to do is work on vacation. And there are a ton of distractions. Be distracted. Good ideas for stories don't happen while you're staring at a blinking cursor and a blank page. Get out and enjoy yourself. You're way more observational when you're on vacation. Take in the scenery. People watch. Mentally collect all the details to take back with you so you can write them down.
=Look for down times. You do a lot of waiting while you're on vacation. While you're on the plane. Waiting to board. While everyone is getting ready to go out for the night. Before you go out for the day. Little five minute writing sessions add up over a week.
Set small goals. Don't go into vacation thinking you are going to get "a lot" done. Don't set a goal or make up a challenge. Non-numerical goals work best for me, like, "I just want to finish this scene" or "I only want to get this piece of dialogue out of my head."