No they do not. they only have to read your Miranda rights, and be sure you understand them, if they wish to question you about possibly incriminating matters after you are taken into custody. If you are not in custody you can just refuse to answer. If you are in custody you don't have to answer either but you have to have the advisement of rights and access to an attorney if you want one.
Many people are confused about Miranda warnings and what the consequences are of a failure by the police to give them. The US Supreme Court described the requirement for Miranda warnings to be given as a "prophylactic" measure. They were intended to protect against abusive interrogation techniques. A failure to give Miranda warnings, after someone is in custody, can mean that any statements the person in custody made (that are self-incriminating) cannot be used as evidence against them. However, the failure to give Miranda warnings does not mean that an arrest is unlawful. This is quite different from the situation where a police officer stops someone without reasonable suspicion or arrests someone without probable cause. In those situations the charges may end up being dismissed or evidence that resulted from the seizure or arrest being supressed.
The better answer is that is depends. Typically any conversation you have with the police, at least in California, will be considered a consentual encounter. Besides, failure to know the law is no excuse, because all are deemed to know the law.
The best approach is to politely state that you reserve your right to remain silent and that you would need to consult your lawyer so you don't say or do something that could incriminate you. Then immediately contact a