To answer your questions, I suggest you visit our Membership page that includes all the details.
Portland is one of our corporate locations and you can utilize your credits there as well as the $39 per additional day.
Salt Lake City EagleRider is a franchise location and at the moment does not accept membership credits, HOWEVER you can still take benefit of the 15% discount off the retail rate.
"15% Off for Additional Rentals During Blackouts and Non-Participating Locations"
Retail Rental Specialist
EagleRider Los Angeles