Is it reasonable to say, "Please take good care of valuables and take no responsibility for their loss"?

Whether the statement "Please keep valuables properly and take no responsibility for their loss" is reasonable or not must be judged in combination with specific scenarios. If it belongs to the agreement between consumers, it violates the mandatory provisions of the law and is directly invalid.

Law of the People's Republic of China on Protection of Consumer Rights and Interests

Article 7

Consumers have the right to protect personal and property safety when purchasing and using commodities and receiving services.

Consumers have the right to demand that the goods and services provided by business operators meet the requirements of protecting personal and property safety.

Article 18 Business operators shall ensure that the commodities or services they provide meet the requirements of protecting personal and property safety. For goods and services that may endanger personal and property safety, consumers should be given a true explanation and a clear warning, and the methods of correctly using goods or receiving services and the methods of preventing harm should be explained and marked.

Operators of hotels, shopping malls, restaurants, banks, airports, stations, ports, theaters and other places of business shall fulfill their obligations of safety protection for consumers.