Jane,

I think Foxwoods goes to 23 or 24 in their current set. They have two single zero tables in the one high limit pit that use a 36 and 38 I think.
The Mohegan Sun set doesn't include all letters up to Y yet.
Can't find my notes to give an exact amount at either but I think they have about the most tables.

Caesars AC has used a Roman numeral XXII but doesn't have 22 tables.

BriaN