AFAIK, schools are out, unfortunately. I do not see any exceptions to the state laws against firearms possession at schools. (NRS 202.265)
Polling places elsewhere would be good to go, and if one were to try to give you grief over it, please get it recorded. It might be a serious crime to interfere with a voter.
If a private business opts to be a polling place, I don't see how they can enforce trespassing on a voter while that person is directly involved in that activity on their property.
Here is the law on voters' rights: NRS 293.2546
Honestly, I think one SHOULD be able to argue being armed at a school while voting. But I will guess that it might take a couple courtrooms before that right is hopefully affirmed.