TRIMET.ORG
will save you tons of time and effort. Play with departure times and routes and you can coordinate trips that drop you nearer home/destination, require no transfers, arrive you earlier, etc.
But a scooter will save you way more money than a bus, and more time and flexibility than a car! You still have to pay for parking for it downtown (wtf? they should be encouraging use!), but you can always slip into the best parking spots with ease.