Is it acceptable to refer to 'patients' as 'clients' or should they always be called 'patients'
and 'men and women' as 'males and females'?

patients over clients: your choice. It depends on what you're providing too. If you're providing a personal service, use "clients". If you're a nurse on a med ward, use "patients".

men and women and males and females: Again, it depends. Use the latter for loos, but there's a choice.

We need more context to answer this, I'm afraid.

i saw ablack filly in my neighbour's farm