I would second not staying at the Hilton .. it is mediocre... I did enjoy some Hilton's so I am not Hilton bashing (ie the Hilton Milenium in NYC is awesome!! as is Cancun).. But for Portland, I highly recommend the Westin (I know Starwood).. the hotel is pretty amazing and comfortable... if you cna get a good deal.. snag it!!
Good luck!