Ok, so I'm biased due to my pseudonym. Nevertheless, I recommend Québec City. It's very romantic, albeit very cold.

However, I believe Valentine's Day weekend is the closing weekend to the Carnaval d'Hiver, as mentioned above, which is a very popular event. Getting a room may be very difficult as it is now so close to the weekend.

I have a room reserved for the HOTEL DOMINION 1912 on the evening of Feb 15 at the rate of C$189. I don't plan to use it. If I can transfer it to another person, you can have it. The hotel is located in the center of Québec City.

Otherwise, Ottawa is very charming and there's lots to do including the Musée du Civilisation across the river in Hull.

But whichever city you choose, you come out a winner on two counts: The restaurants in both cities are great and the Canadian dollar is still weak (can't say that about the € ).