This year’s Worldcon, MidAmericon II, has issued the site selection ballot for the 2017 NASFiC. This allows WSFS members to decide which of the two competing bids (San Juan, Puerto Rico or Valley Forge, Pennsylvania) will host the 2017 North American Science Fiction Convention. A NASFiC is held in North America when the World Science Fiction Convention (Worldcon) is outside of North America. The 2017 Worldcon, Worldcon 75, is in Helsinki, Finland.
You can download the ballot, and also information posted by the two bids, from the MidAmericon II website (scroll down past the information about the 2018 Worldcon site selection).
You can only vote in the site selection election if you are a current Supporting or Attending Member of MidAmericon II. In addition you will need to purchase an Advance Supporting Membership of the 2017 NASFiC. The price of this has been set at $35 by agreement between the two bids and the administering Worldcon. Voting in site selection automatically makes you a Supporting (non-attending) member of the 2018 NASFiC. You will be able to upgrade that supporting membership to an Attending membership of whichever bid is selected after the votes have been counted.
For NASFiC purposes, North America includes Hawaii, Central America, and the islands of the Caribbean.
Further instructions are available on the MidAmericon II website and on ballot itself.