it is prohibited. They did not. So what message were they sending by discouraging it? Obviously, we should take that into consideration and we should think about what activities will be done and how they will be done while still within the mission boundaries.
When my parents came to get me, I wore my suit until we left my mission area. I behaved with dignity. Then I went more tourist mode (but pretty close to a P-day missionary) the rest of the trip.
I think it's great that people suggest going back later. In a case like South America and a family like mine, there is no way that was ever going to happen. It was either then or never. Setting aside the time and money wasn't going to happen unless it was then.
My son that is currently on a mission says it is prohibited by his MP. He'll get a new MP before coming home. If the policy doesn't change with the new MP, we'll respect it without complaint. If it changes and my son wants us to get him, I'll be very likely to do it.
With my son who just got his call to my mission, I'll have a hard time not coming to get him if it's allowed.