My Spirit flight will arrive around 11 Pm, I will call Holiday Inn for shuttle service. Where I should wait at airport to meet the shuttle bus?
Yes, the second island between traffic is the hotel shuttle pick up/drop off spot...but call to make sure they know your there.
There is an area outside of baggage claim where the shuttle busses for the various hotels pick up guests. There is a customer service agent down in baggage claim who can tell you where to wait for the shuttle. Also, when you call Holiday Inn ask them where to pick up the shuttle.
Get an answer from Holiday Inn Portland Airport (I-205) staff and past guests.