Although most people would wear "dressy casual" to a museum, no one really cares, and people do wear jeans. As far as packing goes, I would recommend a pair of khakis made from some kind of light-weight wrinkle-free fabric. They’d look nicer, and you’d feel better on hot days.

I too would opt for the khakis over jeans. But if you really like jeans, I suggest taking a nice "dressy" pair— new and in a sharp, dark color.

im just back so travelled thru vienna prague and croatia
it was early june
vienna was cold
and drizzly
so i wore jeans and black moccasins.. i wore a long tshirt a light sweater a fleece jacket and a fleece pashmina ( that was the best thing i packed and i wish id taken another just so the photos looked different)
my guy wore a long sleeve polo shirt and a heavy waterproof jacket ( hes originally from canada and im an aussie who feels the cold)

in prague i wore the same combo ..stripped down once to my long sleeve tshirt but then wed turn a corner and it might be shady or cooler so the sweater would reappear

by croatia i was in my khakis ( dirty olive colour)..what a difference a few degrees latitude makes
they were brilliant
the most comfortable ever
they werent too low and they had a sash belt so i could tighten them anyway but the other pair i packed were far too low and got too loose so after hitching them up constantly i put them in the bottom of my bag and that was it

i wore my old white runners the whole time in croatia…and my feet loved me for it..i walked up hill and dale..conquered the steps of dubrovnik and coulda danced all night if my man hadnt collapsed ( his new walking shoes werent as well built in the arch and he felt the pressure)
talk about dancing…that croatian music can be real boppy stuff…its either all romantic or real thigh slapping stuff..u cant help tapping to it as u tune in channel dubrovnik lol
mind u
plitvice lakes were freezing and raining quite heavily ..my raincoat couldnt handle it and we were both drenched up to the thighs..so we were glad to have a spare pair of shoes and pants to snuggle into..we hung out our wet gear in the car as we drove to the sunnier coast of dalmatia
and forget about what everyone says about packing minimal stuff as far as undies go…they dont dry …i repeat…if u dont take enough for a week..socks and underwear ,..then be prepared to go dirty ..i hung mine out for two days and they were still damp ish
i refuse to wear socks two days in a row and , girls… u know what it’s like when ur travelling with a guy ..u wanna be fresh…THEY dont care as much lol…just watch them sniff those socks and happily put them on yet again!!!!!!!!!!!!!!!!