Let's make one thing perfectly clear about the Boston Red Sox and the Baltimore Orioles. These people do not like each other. 40,000 people at the game. It was roughly a 50/50 split amongst the fans.
I sat with my family in the LF seats about 5 rows up. Fair warning to all: Do not try to eat food in the LF bleachers at Camden Yards during batting practice. It's kind of like a 1 hour snowball fight where only one side is throwing snowballs. We sat 5 rows back from the outfield fence. We had to keep our heads up the entire time. My grandfather actually had one ball headed directly for him. Thankfully, the guy standing in the row in front of us got his hands on the ball and deflected the ball to the side.
One very large Boston fan (375+ lbs.) started running some smack after the Red Sox took the lead. That wasn't taken well by the Baltimore fans. One guy fired off 'The buffet's behind section 70, buddy!'. Another guy said, 'I'm surprised you could even stand to talk that smack!'. A third guy said, 'Ladies and gentlemen, the 2006 Coney Island Hot Dog Eating Champion!'. I'm ashamed that I chuckled at the last one. The fans did unite together in an occasional 'Yankees suck!' chant when the proceedings got a bit slow.
If you get a chance to come to Camden Yards, be sure to go see the Babe Ruth Birthplace Museum and the Sports Legends Museum (combo ticket runs about $13.00). Well worth it. A lot of great stuff. My favorite part was a display where you could actually handle bats used by Babe Ruth and Cal Ripken and compare the bats from the different eras.