Anyone (except House of Blues) would be good in my opinion, these are my thoughts on them specifically:
L'Originale Alfredo di Roma- Been a while since I have been but from what I remember it was very nice, I went on a date and can't say I was dissapointed.
San Angel Inn- romantic (kind of dark, all by candlelight overlooking the Mexico boat ride)
House of Blues- Kind of loud, informal not too romantic
Wolfgang Puck- the actual resturant (obviously, not the quick service)... very nice. I enjoy it a lot. No mood lighting or anything, but quality resturant.
I know that probably doesn't help you to make a decision so perhaps someone else can narrow it down, what my point was is that I don't think you would be dissappointed in any of them (except HOB, good food, but for lunch maybe one day)