Where should you not propose to someone. Of course there is always exceptions but, there are a few places that should generally be avoided.
You want to make sure your message is heard so avoid really loud places like a rock concert or air show. You might be able to make these places work but keep the logistics in mind.
Another persons big event like a wedding should be avoided. Seems like a great idea but, it is their special day, and it should stay that way. You don’t want to but into someone else’s parade. Anything that is someone else’s day likely isn’t a good place.
Any very uncontrolled environment. Although you don’t need to control every aspect of the place you want to know that someone isn’t going to come interrupt while you are about to get down on one knee. A busy restaurant could be an example of this. Unless you have everyone in on it then u could get bumped or interrupted being asked if u need more bread. Where as a small quiet restaurant where you had your first date can be more easily navigated.
It’s all very dependant on what you want. These are not stead fast rules, just examples that can make you think about the logistics of proposing.