CNN states that there were about 1,000 Bush supporters. Later in the article it says that more than 1,000 showed up to support Sheehan.
Fox’s AP article says that there were several thousand people with “most in a caravan for a pro-Bush rally.” They later estimate the pro-Bush group at 1,500. For Sheehan’s group Fox says “Organizers estimated the crowd at more than 2,000 but it appeared smaller.”
Links to the articles: