If I really, really wanted to pick someplace incredible, I'd be looking towards The Maldives, personally But it can get rather pricey I'm sure, but can you really put a price on romance?
Kauai, known as the Garden Isle, is just as other posters have said. Gorgeous, romantic, perfect weather. All things as tropical as you like!
Having lived in and around San Francisco most of my life, I would never recommend someone to NOT travel there! There is no City like it anywhere. There is so much to do and to see that when the trip is all over, you'll already be planning your next visit back. The weather in August should be very nice. If you do head up north, wouldn't you rather be driving? Say, up the Pacific Coast Highway and spend a night or two in Carmel or Monterey on your way? See Hearst Castle in San Simeon and the Monterey Bay Aquarium? Ahhhhh.....I know so many places I would love to show you both! Tis almost a shame I moved away and can't be your personal tour guide.
No matter what you decide to do, I know you'll have the time of your lives. Happy honeymooning to you both and congratulations!
