The good news is that the Falcons' biggest strength, passing the ball, goes up against one of the Chargers' biggest strengths. There's a reason that teams don't often complete long passes against the Bolts, and that reason is Eric Weddle. There's also a reason that Tight Ends don't do much against San Diego either, and that reason is Donald Butler. Expect to see lots of passes to RB Jacquizz Rodgers in this one.
The Chargers run defense has been even better than their pass defense this year, but that seems mostly by choice. What I have noticed, and this isn't exactly a weakness but it is something that will have to chance, is that the Chargers leave opportunities for QBs to run with the ball far too often (see Jake Locker's 20 yard run last week. Matt Ryan, despite being an awful lot like a younger Peyton Manning, is quite fleet of foot and knows how to slide at the end of plays to pick up penalties as well (take not, Vaughn Martin).
In his 4+ seasons in the NFL, Ryan has rushed for over 400 yards and 5 TDs. By comparison, Philip Rivers had rushed for just over 300 yards and 3 TDs despite starting 32 more games than Ryan.
Matt Ryan is actually the only "runner" on the Falcons averaging more than 2.6 yards per carry. Against the Broncos, he ran 6 times for 19 yards. That doesn't seem like much, but his ability to pick up first downs with his legs will need to be factored into the gameplan. San Diego's Defensive Coordinator, John Pagano, will have to make sure that any pass-rush comes with a spy in front of the pocket to keep Ryan from making plays with his legs.