I use the term lady in a deferential way, referring to someone I don't know. I don't particularly like the collective ladies it just smacks of twee and quaint, although I can see women sounds a bit bald, not in the lacking of hair sense, just somewhat blunt! Nevertheless, that's what most of us are unless of course one is married to a Sir. I'd never call out anyone else for using whatever their preference is though, it's just not mine. I just prefer plain old men and women. A friend of mine was inclined to say, when our husbands were golfing together "I wonder how the boys are getting on?" so much so, I felt inclined to say on one occasion, "boys are you having a laugh? that ship sailed well over half a century ago". Collectively, I don't mind "guys" it may be colloquial but I'm just so used to children and grandchildren using it when talking to both of us, by extension I don't mind it at all from waiters or anyone else who happens to be serving us.