Is there still harmful radiation at the Nevada test sites, ground zero?

Yes, although, similarly to most of the Chernobyl area, the radiation levels are not high enough to pose a risk on a short visit, which allows tours to be held, facilities to operate and training in realistic radioactivity tracking and decontamination work to be conducted (numbered areas 1 and 11).

Several areas (among them numbers 2 and 3) still have significant surface plutonium concentration.

https://en.wikipedia.org/wiki/Nevada_Test_Site