Unloaded open carry (UOC) is not very common and will likely attract law enforcement attention. Under PC12031(e) police are authorized to conduct a loaded inspection. Refusal to allow the inspection is cause for them to arrest you for carrying a loaded weapon. They may step over the line and demand ID or run serial on your weapon- absent reasonable suspicion, this is a 4th amendment violation.
You also should know that California has a prohibition to carrying within 1000 feet of a school (PC626.9). A locked case is an exemption.
Carrying in a hospital may be illegal- it depends on whether the hospital is considered to be a public building according to PC171b. This would be a building where public employees conduct their business.
Police reaction to open carry varies by location and department. Some have been detained for several hours- others for only as long as it takes to conduct a loaded check. Some have been drawn down by police, others have not.