One trip, they never sent me a text and I went back to the desk at 4 to check on my room.
I don't know if Excalibur has it, but the Mirage (same ownership) will check you in and then send you a text later when your room is ready. They will most likely completely do your check in, but you won't have a room assigned, possibly till 3-4 in the afternoon unless you pay for early check in, then you'll get a room assignment around 11-12. I have checked in at 8:30 AM before with no problem. Then go to the registration desk to check in. You can go straight to the Excalibur (which is what I would do, since it's near the airport and I don't want to mess with my bags) and check your bags with the Bellhop. Early check in usually means they actually put you in a room early.