I have never had much luck syncing audio with video from a different source without putting more work into it than what was justified by the finished product. I am sure others are much better at it than I am, but it is just more of a pain that naything... I prefer just laying some ambience or music over the sound that is already in the video, or just muting the video all together and tossing music onto it.
Also, for any kind of Con where you will be doing interviews, I say you DEFINITELY need something like the XL2. The more professional the camera looks to the interviewee, the more serious they will take the interview. Less people simply shouting in the camera for no reason... and more people who otherwise wouldn't do the interview, will take you seriously... it is a sad but true fact, the look of the camera adds credibility to what you are trying to accomplish.
If you simply want something small and cheap that takes a nice steady shot, and has an external mic port, the Canon Vixia HF100 is a heck of a good camera, and is usually in the $700 range... but I can guarantee no one will think you are anything but a blogger if you shove it in their face... may as well use a cell phone
If he XL2 is what you want, but you can't afford it, you can usually find an XL1S on the used market for a fairly good price. It is basically the same camera, but you get less control over framerate, less optical zoom, and shorter battery life. Another thing I have heard, is the white balance and saturation is better on the XL2, but I know how subjective such claims can be, so until I see a professional review comparing the two with definitive results, I will just stick to the facts
