Those activities are governed by state law, so it does matter where you are. I'm not in NM, but a Google search produced this summary from your Gaming Control Board:

Gambling Review

I'd look that over, explore their site, and then call with specific questions. They should be used to helping organizations like yours understand the law.

Does anyone know who I would check with to find out if it is legal for a PTO to run a raffle?

I'm in NM if that helps.

Thanks.