I'm with Mom2Melli.
Northern California here, and also took a 2 week vacation in PI to visit wife's family last year.
I would suggest monthly bathing for general cleanliness, smell, etc. If dog shampoo is expensive, you can use baby shampoo with a little Baking Soda (ie. Arm and Hammer) to raise the pH a little bit closer to dog normal.
Mine gets one every 1.5-2 weeks simply because he plays at the dog park almost every day, and it builds up.
I also have a small wash basin to wash his feet in with soapy water, and a garden hose to wash off his butt when he's eaten something that makes a mess.
A spray bottle with water and shampoo works great and saves a lot of shampoo too.
Also, considering the heat in PI, the occasional water only shower/bath might be a treat in your dogs case.
On a related note, I've noticed my guy loves to be cool, and is totally enjoying the 50-60 f temps we're having right now, so I am going to take a spare piece of granite I have left over from a kitchen remodel and make him a nice cool spot to lay on in the living room. Place it directly on my wood floor and let it stay closer to the ground-concrete slab-wood floor. Thermal conduction should mean that it is always the coolest place in the room for him to lie upon. With your heat, you might be able to do similar with a thick piece of tile or such.
Dogs don't really sweat, they primarily cool themselves by panting and cooling via the foot pads. Any assistance you can give there, or with a small fan maybe, will definitely make your dog much happier.