Well, one year it was the day before V-day and I had no girlfriend or date set up. So, the day before, I went to the online dating site I was signed up with at the time, saw a hot chick, and hit her up with the following message:
"Hey there... so, this is gonna sound kinda odd, but... since we're both on this site, I assume it means neither of us have a Valentine for this year. What's say you and I go out on a date? Nothing too big, but just a nice date so we can both get out and have a good time on that day. If interested, lmk!"
And the next day, I had a Valentine's date.
In short: it's not hard to get a date on Valentine's day - most women want to have a story to tell their girlfriends about going out and doing SOMETHING - so just play to the woman's desire to not want to be seen as a dateless hack and you should be fine.
As far as going out: I don't know where you live, but there are a BUNCH of single's mixers happening here in Los Angeles tonight. Go to YELP.com and look up "single's mixers." If you live in a big enough city there should be SOMETHING going down. And if not, most bars are having V-day drink specials and/or single-stem roses you can buy. Go to a bar and use those items to make a game out of it - something like "What will you do for a rose?" game, or "V-Day drink special shots" game, something fun that will make you stand out and have her having a good time.
Hope this helps!