Google says yes...they were on in 2009. The Cowboys have also been on twice, in 2002 and 2008. That makes half of the seasons of Hard Knocks coming from 2 teams as this is the 8th season of the show.
Most teams don't want to be on the show, understandably so, but it seems as if the Bungles enjoy it since it'll be their 2nd appearance in 5 years. Would absolutely love to see the Pats on Hard Knocks but there is absolutely no chance of that happening.
I just would like to see the Pats, simply to get a glimpse into that team and their day to day operations, so to speak., I feel they are the best run organization and the best coached team in the NFL, and it would be interesting to actually "see inside" the machine. There's not a chance in hell that Billy would allow that type of access though.
I don't know how early they ink those deal though Twink. I think it takes them a while to even get a team to commit to doing the series, as they get turned down by most teams. Even the Bills turned them down a year or 2 ago, which made zero sense to me as the Bills (and other teams like the Jags, Browns, Bengals, etc) can always use the exposure and should welcome it. It seems as if the Bengals agree since they're doing it again.