I travelled a lot with my old dog, a 80 lb. Belgian shepherd mix.

Never had a problem with a motel not letting her in because of size. The two questions where “whether” and “how much.”
A fair number of motels don’t allow dogs. Of those that do, most charge a fee, ranging from $10 to $25. One place I stayed at on 101 in northern CA was run by an Indian family. The clerk made up the policy on the spot . . . $15 in cash, which probably went into her pocket.
A few places I stayed at charged a deposit. Only one required an inspection before I got my $20 back. They were really nice about it. Afterwards the staff petted Kira and gave her a take-away box of breakfast ham and bacon from the buffet. I’ll admit having a stick or two of the bacon for myself.
I’m driving down to the Bay Area with my new shepherd, Ivory, in a couple of weeks. Time to start looking for a couple of motels along the way . . .