Listen to Dale and not all the guys telling you it would be weird. I don't think a message board is the best place to seek advice on this. It's not a stretch to say that a lot of people spending their whole day playing on the internet are just a bit socially awkward and that their reactions in these social situations are not typical.
While I fucking suck at hitting on people, I think I'm pretty good at putting people to ease and getting them to talk, when I want to. As you said, you have mutual friends and interests that are a reason to approach these guys in the first place. Get them talking on a subject that interests them (should be easy at SXSW, right?). If you find what they are saying, TELL THEM. It's as simple as saying that's interesting / that's cool / etc, and 1) letting them know they're not boring you to death, and 2) flattering them a bit by being impressed by their tastes / knowledge / etc if appropriate. Once you are sure the guy is interested in having a conversation with you, it's easy enough to get a date-like situation out of it: I've really enjoyed hanging out with you, would you like to get a drink later? dinner tomorrow? etc.