I mean, Raijinken has some solid advice there, but I don't think there's any harm in going and playing your first time. It beats standing around and watching. Isn't that what you're there to do? Play the game? People are mostly pretty nice and will probably give you tips after or during your matches. Questions are fine, try not to overdo it, but that's something you can feel out; it's just dealing with people, standard stuff. Of course, there may be some jerks, but that's normal. Don't pay attention to them.
Just showing up and participating is enough. Have fun. If you want to learn, there are plenty of ways to get better while you're there, you just have to put yourself out there a bit. But be careful, of course. These are strangers, so you should know the drill. Watch out for creeps, play as much as you can, ask questions, have fun, or keep to yourself and mostly watch other play, whatever. It all really depends on what you want to get out of it. Big thing is working it out with your parents and being smart about things. Hope it all works out!