My DH is British, and his family were always shoes off in the house. Which I of course didn't question, until the first time I visited I realised I couldn't survive there without several pairs of thick woollen socks at least, they never had heating on and had hard flooring downstairs.
I never could understand carpeting all over downstairs, just seems too high maintenance, so we always had hard floors, but because houses are noticeably colder than in my country of origin, I do wear indoor Uggs in the house in the winter, and in the summer it's sandals. Though I kick them off for at least half of the time, and walk around in socks or barefoot in the summer or if the living room if it gets really hot with the fire going.
Everyone who comes to our house, either automatically starts taking shoes off, or asks - but actually nowadays I say no need, keep them on! But nearly no one ever traipsed in their outdoor shoes upstairs, most people take them off before going up, unless it's really dry summer. We actually have hard flooring upstairs except in the extension bit, but the stairs are carpeted with sisal which seems to work as some kind of shoe brush, cleaning the soles of people's shoes perfectly but itself near impossible to clean off. 
We do have efficient for shoe wiping coir matting in the porch, but not everyone visiting makes use of it.
Basically, I think most people who call their households "shoes off" mean no outdoor shoes, but no one would mind if you brought your own (if you hate the idea of guest shoes/slippers, also common in my home country) clean indoor footwear! Which is a perfect solution for any party, you either do jump from the car to the door in the clean party shoes, or you just change into nice clean dressy up shoes, I can't imagine any shoes off household not letting you do that, unless they have precious wooden floors and you are wearing metal heeled stilettos!