Unfortunately there isn't much ettiquette on public land. I've always hunted public land and run into people at least twice a year. Normally one out of the two "meetings" ends with a "My bad, didn't realize you were here. They've been coming out at about blank time, good luck" and one of us walks away. The other one usually ends up with someone doing a drive (during gun season) or still hunting right through my setup. I have a general rule where if I see vehicles parked at a spot I wanted to hunt, I move on to the next spot - but I hunt several small parcels of public land that can't really be hunted by more than 1 or 2 people.