Just some observations to pass on from what I saw in the early evening yesterday and daytime today -
Mandalay Bay has a designated Uber/Lyft pickup at their main entrance. Follow signs to Registration and stay left of the large columns (might be shuttle buses in that area to help you find it).
At other hotels, follow signs to either "thru traffic" or "hotel registration" to get closer to the doors. Don't follow the cabs. Valet & security have been pretty nice in places I've pulled in. But locations may change (like designated areas) as things get moving.
I see a lot of drivers wasting gas driving around waiting for a ping. Check out Industrial, Dean Martin or Koval in between pings. There's places you can park without getting crap or mingling with cabbies. Downtown there are a couple of side streets that have 1 or 4 hour no meter parking.
If you have anything to add or correct, let's work together via this thread so hotels will stay happy and we don't become a hassle.