I'll be there and be loud!
If the last home playoff game is any indication, there will be very few opposing fans. Last time, when we played the Eagles, it was a week after the regular season conclusion which was also against the Eagles. During the regular season finale, there were a good number of Eagles fans at the game... maybe 20-25%. At the playoff game a week later, I'd guess it was closer to 5-10% Eagles fans. It's just tough for opposing fans to get tickets and book flights with the short amount of time to prepare before a playoff game.
I can't imagine that Detroit will travel well, so I'd guess something short of 10% Detroit fans, which should make for an excellent home-field advantage for the Cowboys!
Biggest thing will be the Cowboys coming out of the gate strong and giving the fans a lot to cheer about.