Lions/Chargers was the last game I attended at Qualcomm and it wasn't a bad game. Chargers spanked Detroit but there were no malicious fans at that game- those wannabe thugs exist as real thugs in SD but most don't usually attend the game. If you manage to stay away from Logan Block, 43rd and Spring Valley you should be good.
I will be making the 45-minute drive down to San Diego to watch our Pack if the CBA neg allow for it. I have friends that drink like fish and all love football so tailgating is always priority (park near an exit) and be sure to be there early- Cali traffic sucks.