When you decide to go for a riding vacation, plan to embark on a conditioning program 2-3 months or more before you head out. Find a good stable with an instructor who caters to adult learners, and ride at least once a week.
You will enjoy your riding holiday so much more! It can make the difference between being happy and relaxed on top of a happy mount as you admire the scenery and wildlife, and being hunched up in agony on an irritated horse, trying to keep the tender bits out of contact with the saddle and praying for the ride to end! Not to mention being unable to walk the next day . . .
When I don't ride for a week or so, I pay too . . . :-p