Yeah, I was telling my mother about the movie and trying to remember my Texas history... Geez! Now that I think about it, I don't think the movie exaggerated much. Historically, it is pretty accurate.
Like Bear said, there were about 180 men, against (I thought it was 10,000 Mexican troops) 5,000. Sanata Ana was trying to save face since he had just had to turn tail after a hugh defeat 6 weeks prior. He *knew* that there wasn't a big garrison at San Antonio, and yet he sent his entire army there to capture/claim it. Santa Ana thought he was Napoleon or something like him.