Disclaimer: This answer is based on a layman reading of the text of Chinese law freely available on the internet. This is obviously not an legal advice.
If you are staying in a hotel in China, the onus is on the hotel to get you registered and pass your information to the police.
This stems from Article 39 of The Exit and Entry Administration Law of the People’s Republic of China (中华人民共和国出境入境管理法 第三十九条). From the website of Chinese Consular Affairs:
Article 39 Where foreigners stay in hotels in China, the hotels shall register their accommodation in accordance with the regulations on the public security administration of the hotel industry, and submit foreigners’ accommodation registration information to the public security organs in the places where the hotels are located.
For foreigners who reside or stay in domiciles other than hotels, they or the persons who accommodate them shall, within 24 hours after the foreigners’ arrival, go through the registration formalities with the public security organs in the places of residence.
It is an offence for hotels that refuse to do so. The particular law in question is Article 10 of Provisions of Guangdong Province on Administration of Public Security in Hospitality Industry (广东省旅馆业治安管理规定 第十条), from the Baidu (Chinese Wikipedia) entry (rough translation mine):
第十条 旅馆应当如实将旅客身份证件信息录入旅馆业治安管理信息系统，并在旅客入住后3小时内传送到旅馆行政区域内的公安机关。尚未建立旅馆业治安管理信息系统的旅馆，应将住宿登记表于当日送旅馆行政区域内公安机关。旅馆应当妥善保管住宿登记表册，保存期1年。
Article 10 Hotels should record guests' ID on the Administration of Public Security in Hospitality Industry Information System, and send the information to the police within 3 hours of the guest checking-in. Where such system are not built/implemented, hotels should present the registration form(s) to the police on the same day. Hotels should carefully retain the registrations for a year.
According to Article 21, the penalty (for the hotel) is a RMB 1,000-5,000 fine, subject to probation.
