We are taking our 5 and 3 year old to SD the first weekend of March and are tentatively planning to go to Legoland on Saturday. We will be there all day. How bad will the crowds be?
I'm not going to be a huge help, but we just visited on December 9th, a Sunday, and it wasn't real busy at all. I would think (just a guess) that a weekend in March wouldn't be that different since kids are still in school, but only a guess.