FYI, the "day before" is generally a work day, and those showing up in the past two years that early were there to work. I won't say that a working volunteer or two didn't take a break and flew a battery, but they generally went back to working after their break.
I can't say if anyone will approach you and ask you to come back later if you come early with no intention to work, but it's somewhat rude to spend the setup day playing and partying while everyone else are volunteering their extra day working around you, setting up for the whole festival.
They paid to be there too, and they're still donating their time and labor to make it a great event. Getting in their way and goofing off while they're working, where they're working is insulting, and I'd ask you to please treat them with better respect.
Now if you want to work, please, show up and pitch in. You won't find a better group of people to hang out with.