I go with the favorite place approach..But..It's the technique..True,the more public,the better,but a woman wants to know why he wants to marry her.I think it's more in the way he will ask,than where he asks from.Giving a quick recount,of how she went from friend,to being special,to being the light of his life is the way to go from my point of view..
And tell him to wear a wire,to tape the second of silence he gets when he drops to his knee,it's the last silence he will hear as she goes into the "planning" mode for the wedding,lol..
I'd be willing to write him a poem,if he wants to do it that way..

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As long as there's feet at the bottom,and Pussy at the top,They're ALL perfect Legs