Thanks all for the input. Ended up working out just fine, no questions asked.
Newbie - thanks for pointing out the train option (I did see it after I had posted this thread). I probably would have given it a go if the car didn't go through.. dreading the day stay in the WC (which turns out closes at 4 pm plus or minus). Car option worked great, though - $16 a/i for a Subaru Forrester.. can't beat that for cheap.
Had a great time - did Nob Hill, Saturday Market, Tram, OMSI and Niketown (sorta) - as well as a leisurly drive through the hills. Next time.. Mount Hood.