neas,
Welcome to ScubaBoard!
Based on your post of the statement from their website you'd be reasonable to talk with a manager about getting a refund of the cleaning fee. If that conversation went poorly, I'd be inclined to take my business elsewhere.
But as others have noted, not all shops have rinse tanks available. I suspect it comes down to how close they are to the dive sites. As the salty gear dries, the salt crystals begin to cause damage -- especially to neoprene. It's best to not let the gear dry until it is rinsed. If a shop expects you to return the gear the same day you rent it (as is often the case in Monterey), then they probably have a place for you to clean it. But, if most of their rentals get returned a day or two later (as is the case in the Bay Area), then they probably expect you to clean shortly after your dive. Probably it's best to ask when renting (or even reserving) the gear.
Also, their requirement that you clean in soapy water may be unusual. If I recall correctly, the shops I've rented from say not to do that -- fresh water only. I'm not sure soaking a reg set in soapy water is good for it.