You can with the MLB.com At Bat 2011 app. When you purchase it, of comes with a free trial of MLB.tv. You can watch any MLB game in the league. I forget the price of the TV portion, but I know it's a little pricey.
That At Bat app includes streaming radio feeds from both teams home stations. It's about a 30 second delay from the regular broadcast, but for me it comes in much clearer than the AM station.