I would prefer mine on the main level of the house to be near the family and not so isolated (as others have said). I have a 20x20 space with plenty of room for all the quilting stuff plus an old sectional from the 1950's parked right in front of the big TV. The kids (teens) will often come watch TV with me while I'm sewing. The TV does need to be pretty loud to hear it but they will suffer for me.
Mine is in a detached former maid's quarters and I wish it were part of the house. At least it does have a full bathroom so no running back and forth.
This is more than you asked but you are concerned about people seeing it. The easiest way to make it attractive and keep it clean is to not have too much stuff. I have seen some sewing/craft rooms that look like a bad closet and it's a whole room. Mine has looked like that in the past but I made the choice to have a nice attractive room and keep it clean and it's such a joy now. I still need to work on mine more and get rid of more stuff and it will be even better. I usually work on one project at a time. I have to force myself because it's not in my nature. I also force myself to clean up after each quilt is finished. Again, it's not in my nature to keep it clean - it's something I decided to make myself do and it's totally worth the effort. There are very few times I would be embarrassed because it is a mess.
Good luck!