Pam,
Here is a newspaper clipping discussing Ms. Moe the owner of the Hotel Apache.

I have the postcards you are referring to. The angle gives one the impression that the Apache sign with word casino under it refers to an Apache casino. Not so! The bar sign to the left refers to the Apache. The casino word refers to another entity the complete sign of which we cannot see. I believe it is referring to the Boulder Club Casino.

Off the top of my head, I believe The S.S. Rex came before the Eldorado and the Horseshoe sometime in the early 40's.