OK, then. It sounds like you would be best served by a domestic frequent-flyer program that permits a single open jaw on a roundtrip award ticket. So check out those carriers that either by themselves, or with their frequent-flyer airline partners, offer service from your home base to both PDX and LAX (or one of the other airports in the Southern California area), and see which of them permit single open-jaw travel on an award ticket. As I say, I believe that AA does so; you would have to check the award ticketing rules on the other carriers, unless other FTers who see this thread can post the answers. (It might be helpful if you would identify your home airport.)

The Amex Starwood card is probably a good bet if you expect to charge enough every year to make up for the annual fee. If not, then assuming that you have good credit, you might be better served by just taking advantage of the bonus offers that are offered periodically (but with some frequency) by the airline frequent flyer credit cards (like Citibank's AAdvantage cards, Chase's UA Mileage Plus cards, etc.) Currently, if you take both the Citi AAdvantage MasterCard and AAdvantage American Express Card fee free for the first year, and spend a total of $1500 in the first four months ($750 on each card), you will end up with 51,500 AAdvantage miles, enough for two tickets on your next PDX/LAX sojourn, if award seats are available on your itinerary for your dates of choice (that can be a big "if"). At the end of the first year, cancel the cards, and look for an attractive offer from another issuer.