You're going to get conflicting answers for that one. Valentine's day is about 3 weeks away. For me, I could say 5 lbs is a reasonable goal, but that's the way that I lose weight. (Especially since I still have 100 lbs to go.) Some people suggest to forego all "deadlines" as they find it discouraging if they do not attain their goals. You may find it motivating. The only way to know is to try it out once.
A lot of factors are going to come into play. #1. You're just starting out a bit, so you may lose faster right now. 5lbs by Valentine's may be very reasonable for you in the beginning. #2. You don't know how your body loses, yet. This just takes time to get to know your patterns. Unfortunately, I can't tell you ahead of time what they'll be. #3 Our bodies do weird things, so prepare for the fact that sometimes you'll lose a lot less than you think, and other times a lot more. Strange things... these bodies we have.
Now... to answer your actual question!

I think that conservatively, 3 lbs by Valentine's day would be very achievable. 5 lbs would be a little more ambitious goal. (Again, not out of the ballpark, though.)
I cannot emphasize enough, though, that if you do not reach a small goal by a deadline, DO NOT GIVE UP! If you want 10 lbs by Easter and you "only" made 8... that's not a bad thing. That's a very good thing, so it's just something to keep in mind.
If you do make your deadline goals... well then bully for you!

Keep on keepin' on!
Anyway, I hope that wasn't too confusing. >_<