I booked a site at Dorst Creek on the first day the campground opens. I plan on getting there early on the 24th. Check in time is at 12PM. My question is will the campground be closed tell 12PM or will I be able to setup early since its the first day?
For the sake of the employees, since you are booked for a 12pm arrival, don't rush things unless you can call the campground ahead of time and get their approval.
Keep in mind, it's the first day for the majority of staff too and they might need that time in the morning to check out things. They don't necessarily need the public telling them things don't work if they haven't had time to check things over.
I have been there but it was probably 30 years ago in mid-summer. I imagine the first day opens in late May so expect some snow. It's been a heavy snow year all over the California Sierras.
Also bears will be hungry, have just woken up from a long winter, so take care of your food in accordance with their requirements. Call ahead and make sure what they require so you are prepared. Don't wait until you get there, then find out you don't have the right stuff and get turned away. There are big fines if you get caught "feeding the wildlife" whether you intended to or not.
Enjoy your stay!
BTW - I will be in Yosemite Valley around that time. Yell "Hi" really loud when you get there. If I don't hear you it's because I'll be a the Falls and the sound should be resounding. I may need ear plugs since the falls are expecting to running fast, high and LOUD! I love this stuff. I hope I can post some pictures if my camera isn't ruined by all the anticipated spray!