There will be 3 open practices at Qualcomm Stadium in August. Admission is FREE, and Parking is FREE. Sodas and Hot Dogs will be sold for $1 each. There are no autographs sessions on the Wednesday practices, however there will be an autograph session for kids 14 and under on the Saturday Chargers FanFest at 10:15am, as well as an opportunity for autographs after the practices.
05AUG2009 at 7:00-9:20pm Practice open to the public [Parking lot open at 5pm, Gates open at 6pm]
08AUG2009 at 11:00-1:00pm Chargers FanFest 2009 [Parking lot open at 8am, Gates open at 9:30am]
FanFest will feature the debut performance of the 2009 Charger Girls and the debut of the 2008 season Charger highlight film, followed by an opportunity for autographs. Free interactive games will be located on the plaza concourse.
12AUG2009 at 7:00-9:20pm Practice open to the public [Parking lot open at 5pm, Gates open at 6pm]
I wasn't able to determine if tailgaiting is allowed. If you really want to tailgate, I would suggest calling Qualcomm stadium.