Both FSW/FSWE and Univision/Galavison have picked up Concacaf events held in the US at seemingly the last minute in the past, but I don't recall either set of nets ever picking up U-20 quals. In the event that there's no tv, you may want to keep tabs on the Radio Unica or Futbol de Primera radio networks. One of them - can't remember which one now - picked up the games from Hershey for the Concacaf olympic quals in 2000. Can't recall if either of them have ever done U-20 quals, but it's worth checking out just in case. IIRC, El Salvador is the only Central American country in the US group, so there may not be enough interest to pick up the games on any medium.
FSW showed the last u-20 qualifying tourney in Trinidad and Tobago in March 2001. I remember because a trinidad player was paralyzed in a collision with landon Donovan at that tournament.
if they pick it up, it will probably be a last minute thing... just keeps you eyes open on these boards...
Check the US Soccer site's schedule section on a regular basis. They will show tv info, if there's any coverage.