We did the same thing back in '97 - wife had to go to San Fran for a conference. We flew into SNA (closest airport to DL, although LAX often has some great rates), then we flew to SF and flew home from there.
The flights from Southern California to/from SFO are usually not too bad - maybe $100-125 per person. Definitely better than diving (especially with what gas will most likely cost this year!)
For a couple of adults, 3 days in DL should be plenty to see and do just about everything. It does get crowded (especially since the 50th), but if you go early and stay until closing you'll find plenty of times when the lines are short (especially at the beginning and end of the days). DCA is usually uncrowded unless they are doing a 2fer promotion (gives locals basically a free ticket to DCA).
The CityPass is great - gives you DL, San Diego Zoo or Wild Animal Park (if you've done neither, do the zoo!) Sea World, (they are an easy 90 minute scenic drive from DL) and Universal Hollywood (different from its Florida cousin as it is a real studio first, theme park second).
Don't feel you have to stay at a DL hotel (GC is great, DLH is nice and PP is OK). There are clean motels actually closer to DL's gates than the Disney ones. If money allows, the GC is worth the price, but if not, I'd recommend the Del Sol or the Candy Cane (both on Harbor).
Also, check what's playing at the El Capitan -Disney's own theatre in Hollywood, right next to the Chinese Theatre and the massive Hollywood & Highland complex (where the Oscars are held).
The hottest day in Anaheim is nothing compared to the heat and humidity of Orlando. Note even on hot days, the temperature can drop rapidly once the sun sets (causing locals to don jackets, but causing little effect on midwesterners like my family!)
Definitely do DL if you can. It is really neat and actually has a ton of rides (about as many if not more than in all the Florida Parks together). It does have bottlenecks and space issues, making the crowds seems worse than at WDW or DCA, but if you just hang back and watch while the crowds are at their worst, you'll have a great time. It especially looks wonderful right now after the major rehabs for the 50th. The fireworks are amazing (but beware, they are cancelled if the winds are high) and Fantasmic! blows the WDW version away.
If you are going after 6/24, you'll get to see the updated Pirates. Pirates there is literally twice as long as WDW, and features 2 drops - one of them much steeper than the WDW version.