I have to ask: do you go grocery shopping in your barn clothes?
I honestly can't remember the last time I went grocery shopping in normal clothes. The only place I drive is to the barn, so if I have my car out and about, I'm almost certainly wearing breeches. It doesn't make sense to go grocery shopping before the barn, so I go afterwards. I am totally oblivious to the weird looks at this point.
I mean, if I'm totally covered in mud/manure/hay, I will give the store a pass, but if I'm otherwise pretty neat and clean? No question, I'm there.