I know the fraser is a pretty crazy river, but I'm wondering if it would be safe to ride it (the lower fraser) in a 8' inflatable with a 2 horse motor, or are the currents too strong?
Not recommended. I have a 10fter and wouldn't even consider it. If we are talking about the tidal portion downstream from the Port Mann Bridge, strong current takes place especially during the outgoing tide in the South Arm. In addition, huge cargo ships go through there constantly. North Arm is not as bad as the current is not that strong, but there are also big tug boats going by and they cause pretty big waves. Middle Arm is probably the best place, because there are no ship traffic through there. You just have to watch out for floating planes taking off and landing near YVR.
Overall, it's not necessary to be on a boat for pink salmon, because they travel very close to shore. In fact, I would choose to fish from shore if both options are given to me.