We have to put some sort of barrier on our front porch. My husband decided to make solid walls and side them. He thinks 30" walls would meet code. But we should get this confirmed before he builds...

With older people in the house (and as we are in the midst of moving to 1st floor living to age in place) I'd go with level with the door so they could get outside easily. The stairs to leave the porch might be a barrier, but at least they could be outside on the porch.