Yes, you can still do Priority Seating, no matter where you are staying. FYI... We checked during a recent visit and found we WERE entitled to "Extra Magic Hour" which other Non-Disney hotels were not.
PS is essentially reserving a "place in line" for a table. It is not truly a reservation, which suggests you arrive and are seated at the appointed time. Rather, it allows you to tour the parks, arrive at your chosen restaurant, and be put in the rotation for the next available table for your party size. You are behind the others who have PS for earlier times than you, but are ahead of anyone with a PS for later or anyone who comes in "off the street."