If budget is not an issue then you can certainly rent any bike you want ... for a price. IMHO, they are ALL a bit of a rip-off. NO good hire companies. I have met a few of the owners of the San Francisco rental places.
Not my favorite people. For bikes other than HD, try these guys:
If budget IS a concern, why not put out the word on the HUBB community forums? See if you can find a couple good bikes to rent from HUBB members? I'm sure they could beat the $150/day Average rate of Dubbelju?
What sort of bikes you looking for? Most tourists who come to the USA rent Harley's ... thousands every year. We see them in droves in Death Valley, all in Pirate outfits, eye patches and headed to Vegas!
Hey, it's a free country.
You may be able to arrange a buy back from a local dealer ... It may end up cheaper than renting unless you put a ton of miles on the bike. Dunno. Maybe worth a look? Buy a used bike, a slow mover they can't sell. Make a deal.
Or snag a bike on Craig's list, then consign it to a dealer, they send you money once it sells. You go home. Craig's list is LOADED with bargains. You can save thousands against a 21 day rental going this route.
It's more work but could be worth it if on a budget. Set up deal prior to arrival. It's exactly what I did coming into London. Had my bike, all DVLA work done in 3 days after arrival. (lucky)
In San Francisco Bay area I would try Munroe Motors. Talk to Nick, he's a Londoner, one of the owners. Munroe sell Triumph, Ducati, MV Augusta, Norton, Guzzi, Husqvarna. Munroe always have a nice stock of used bikes, wide variety of brands/types, not many touring bikes. Prices are fair.
Also try California BMW/Triumph (Mountain View). Fancier used bikes but good ones ... and they will make a deal. Talk to Carolyn. (a friend ... I bought my 1050 Tiger there)
I know lots more folk in the trade but don't trust them.