We've been there many times in Feb. The weather is usually pretty nice, but it can be cool. The tendency is for the days to be warm, but early am's and pm's to be cool. So you have to go back to your room to put on long pants at night, or wear jeans all day (t-shirt and sweater/sweatshirt layers).
Early Feb is going to be cooler, late Feb is going to be more temperate.
President's week gets a little busy, but not that bad. With all the Disney promos the rest of the year, it probably won't be THAT bad. It is the start of peak season price wise though. You'll pay a lot less if you check in before Valentine's day (not busy).
One thing that makes February fantastic though is just seeing green and palm trees. Especially if you live in one of the colder parts of the country, when you get back you know winter is almost gone. If you go later, you miss seeing 'spring' at home.
March and especially Easter week tend to be considerably more crowded. You'll get the spring break crowd.