I haven't made one yet, but I'll probably end up setting it to either 5am/6am or sometime mid afternoon, with those giant puffy clouds (I forget what they're called rip)
i love the sky around 6-8ish pm, when the sun is gone and everything is all purpley and dreamy! so usually around there, but sometimes in the really early morning when everything is hazy.
but i haven't finished my town, so my dream address isn't updated and so whenever i update my dream it's when i'm in the mood for getting an extra 5k bells, not because my town looks nice at that moment at all! so rn, i'm pretty sure my dream town is set at maybe 9pm, from around a month ago?? when i update my official, finished dream town, i'm sure it'll be around 6-8pm or 4-5am
None of my towns are completed so for now I just upload the dream when the initiative appears... gotta earn those meow coupons... x)
But even still, I tend to save Sundance in the morning, when everything's vibrant (I like the 10 am tune) and Hangzhou in the afternoon, around 5 pm when the sky gains a hint of yellow.