I really think it depends on where you go. When I went somewhere tropical and warm and beachy I tend to bring a bunch of tops and some shorts. If the weather was really nice, and all we were doing was hanging out on the pool deck, I'd just wear my bathing suit, and brought a pair of comfortable terry shorts. They would dry off quick if I got wet, and would serve as something I could either sleep in/ work out in/ hang out in. Most of the time, I wish I had brought more shirts along, seeing how they'd either get dirty or moist with humidity.
In Europe, I saw my self wear more conservative things. I brought more jeans, and replaced the shorts with skirts which provided the same idea, but was a little more "dressed up"
My advice, bring more shirts than you think, and bring the ones that you KNOW you will wear, don't just throw them in because if you're not going to wear the shirt, you'll have room for something else, like an extra pair of shoes.
Skirts can also serve as good lounge wear AND dinner wear...just something ot think about