Moderator, Marriott Bonvoy & FlyerTalk Evangelist
Join Date: Oct 2002
Location: McKinney, TX, USA
Programs: United Silver; AA Plat/2MM; Marriott LT Titanium; Hilton Gold
Posts: 11,776
If your MR# is in the reservation, the hotel should be able to see your elite status. I've never had to show my card to "prove" my elite level.
So while it is probably not a bad idea to have it with you "just in case", it really isn't necessary unless it isn't in the reservation.