Since atdhe.net and channelsurfing.net got seized early this year (although its since been moved to atdhe.ws and should work), it's been a little bit harder to find reliable streams online. For watching caps games last season I mostly used myp2pforums.eu and soccertvlive.net, and they both have sections for football. I'd refresh this page closer to gametime; I bet they'll have a stream:
[Streaming] 2011 NFL Pre-Season - Week 1