At some point before the events of Blade Runner 2049, Las Vegas was hit by a dirty bomb and thus deserted due to the radiation. During the events of the movie however, Deckard apparently has lived there alone and mostly unharmed for years. This begs two related questions:
Why hasn’t anybody looted the place? Apparently it still contains lots of treasures. Whiskey and wood are explicitly mentioned, and the metals and manufactured items probably have some value as well.
Why hasn’t anybody settled there? Granted, it’s not very hospitable, but neither is the rest of Earth.
It doesn’t appear difficult to access Las Vegas: K as well as Mariette and the replicant resistance did not encounter any major troubles getting there. I also would not consider it realistic that nobody noticed that the radiation has ceased, since everybody who can get their hands on a radiation detector (or build one) can carefully check.
As for the radiation, let’s consider the most pessimistic scenario: Only replicants (and bees) can survive living there as well as consuming or using any of the products. Even then, there seems a sufficiently big market for replicants (who seem to enjoy whiskey) and renegade replicants could live there. And that scenario is not particularly realistic since it would confirm that Deckard is a replicant (which shall be uncertain for out-of-universe reasons) and his dog is artificial too (which is an open question in-universe).