I don't think you will find much at all in CA. Even in Detroit, the mecca for RSW there are only around 2 consulting labs. They do not rent out equipment as far as I know. If you want equipment, your best bet might be to try to get some demo equipment from a RSW supplier. But, it you are not serious, you would be leading them on. When I worked automotive, a Chineese supplier once loaned us a complete welding cell for 4 months to "evaluate". They of course were expecting hundreds of orders for robot welders though since we supplied 3000 robots a year to automotive.