With the shops, restaurants, theatres, pubs & bars and free transportation from one end of it all to the other (think of Tri-Met as the world's biggest escalator), who'd choose to go to a mall instead? Downtown Portland may be the cleanest city in the United States, and it's designed for fun and convenience. Best strategy is to park outside downtown and take the MAX light rail in, as car-accessibility issues are downtown's biggest shortcoming.
Pros: convenient, diverse, clean
Cons: traffic, parking