Even some resorts here in Florida have Florida resident specials, which are cheaper than non-residents can get. IF there is such a thing at Mexican resorts, it is irrelevant unless you are a Mexican national. I personally don't have a problem if they want to give special prices to locals. I suspect most places do.

I haven't used them for a long time, but you might check with Go Classy Tours. They are a travel agent I used to use all the time. The only other one that I personally am familiar with is David Parker at All the Way Travel. I'm not sure if David only specializes in nude resorts though.

Best wishes.