A comfy pair of leather walking sandals (check out Columbia Clothing Co. in the states/Canada for a wide range of styles - or LL Bean/Land's End) will take you most anywhere on the kind of trip you're planning. I bought mine (Bama - a german brand) in Lithuania three years ago, and they're about all I wear, all summer long traveling or at home. Can wear them with a skirt, shorts, whatever, wore 'em to walk up Vesuvius and in the woods of Germany, so they're tough enough for some minor off road walking. If you want to take something a bit dressier, a flat pair of sandals are light and easy to squeeze into a bag and are a little less cumbersome on the dance floor! It's not a bad idea to throw in a cheap pair of flip flops for showers and beaches, too, though I can't wear them for long without my legs hurting and I hate having that strap between my toes.
I wear my walking sandals in the rain, but I don't mind having wet feet. If that bugs you, you'll need something weather proof - what about a pair of leather Keds or something like that? I usually wear a pair of leather clogs if it's really wet, but they're bulky.