For me, a perfect vacation looks like this: a comfortable chair in the shade, a view of a lake or the sea, a fruit juice at hand, and a fun knitting project on my needles. Just thinking about it makes me feel cheerful!
But if you want to knit away from home there are some things to keep in mind:
Choose the right project. When it's hot you don't really need a lapful of woolen blanket. Much better to work on a smaller item, preferably in cotton, linen, or any other cool fiber. The project itself should be interesting and fun to knit, but easy enough to be relaxing. Don't pick something you should knit, pick a project you really want to knit.
Take enough yarn with you. If the weather is bad you might get more knitting time than you expected; you don't want to run out of yarn. To avoid an excessive amount of baggage choose thin yarn, if possible. 1000 meters of laceweight are just one small cake but provide hours and hours of knitting entertainment.
Make sure you have the correct needle size(s). If you don't know the yarn yet, better swatch at home if possible, or pack several different needle sizes. It is so very annoying when you start knitting and realize that a different needle size would work better. (Ask me - no, better don't ask me how I know this!)
Pack up all the notions you need. A handful of stitch markers, a crochet hook, a small pair of scissors, a length of silicone tube for trying on the new top halfways - these notions don't take up much room but I knit so much more cheerfully when I have them!
Prepare your pattern. If you prefer to work from printouts, print it at home and take it with you. If you prefer digital patterns things are a little easier, but the WLAN connection at your destination might be wonky, so better download everything you need before leaving home.
I hope these tips will help you to make your vacation knitting a happy and cheerful - and above all, relaxing - experience.
Happy knitting!