As far as snowboarding go, you need to go to Mt. Hood, and Meadows (skihood.com) is by far the best place, great night riding too, and much cheaper than during the day, it is best if you live on the East side so you avoid traffic on the way out. Renting is still fairly cheap around here but buying has become way expensive and it is slowing down so don't buy. There is not much Mountain biking in town, as far as I know, most good stuff in the parks is closed off, again if you drive to Mt. Hood in the summer it is fairly good and a bit further is Bend, great mtbiking there.
Good luck and hope you like it as much as I do.
Ciao
Paolo