Yes I take my kids in public in the summer or warm weather wearing just a diaper.
There's nothing wrong with a baby, toddler or young child wearing just a diaper in public and personally I find it cute to see my little kids that are in diapers out running around in just their diapers.
I used to run around in public wearing just my shirt and diaper and shoes when I was a toddler.
During the summer months a toddler and baby can be much hotter wearing the diaper and having them wear just a diaper or just a diaper and shirt keeps them much cooler.
There's nothing indecent about the toddler or kid or baby wearing just a diaper in public.
The kids are only little once and only for a short time so let them be little and allow them to wear the diaper.
In public they should have at least shoes on such as sandals and I would recommend if the sun is really hot have them wear a shirt to prevent sunburn but there's no need to cover the diaper up.
A neighbor has an 8 year old boy who has autism and he hates wearing clothes and he goes out in his back yard and front yard with just his diaper on.
It does not bother me in the slightest.