Here's an event that separates the nerds from the imposters: Underground Lightsaber Fighters Battle. Yes, it's just what it sounds like: "ULF is San Diego's largest monthly Lightsaber gathering. Every month we hold a tournament for serious fighters and provide a fun place for the whole family and all Star Wars fans to enjoy themselves."
They are holding an epic battle on Saturday night, 23 July, during SDCC in Balboa Park - and yes, you as a Comic-Con attendee are invited to attend. It's free to spectate, but there is an entry fee for the official tournament; however if you just want to fight someone with your light saber, you're encouraged to do that in a non-official capacity as well. Which sounds like a fun Saturday night, if your energy isn't zonked by then after several days of SDCC.
Signups begin in July. If you're interested in fighting, be aware that you'll need more than just a light saber - their page specifies having head and mouth guards, gloves, shoes and groin protectors. Safety first, especially when it comes to Sith lords.