If renters have not paid in a week and moved out everything, can we change locks?

Yes, it is obvious that the have abandoned the premises.

If your tenant has vacated the premises, failed to pay rent, and has removed all of their possessions, AND has failed to give you notice of their intent to abandon the premises, you must properly establish that they have indeed abandoned the unit prior to changing the locks and reclaiming the premises. If you properly establish that the tenant abandoned the premises, this will effectively terminate the lease. Here are the procedures: First, the amount of rent due and owing must have been unpaid for *fourteen* (not seven!) days; Second, you must give written notice of belief of abandonment in the proper format. See Civil Code section 1951.3(b) for the requirements of notice; Third, the notice must be served on the tenant either through personal service, or by sending the notice to the tenant's last known address, or any other notice where the tenant may be reasonably expected to receive it; The notice must state the "termination date" of the lease, which must be at least 15 days from the personal service of the notice, or 18 days from the date the notice is served via first class mail. Because they have left prior to the end of the lease, you are effectively establishing a new termination date for their tenancy due to their having abandoned the premises. If after that period you have not heard from the tenant, the premises can be deemed "abandoned" and the locks changed. If there are items of personal property left behind, there are further requirements for dealing with their property... It's important that the Notice of Belief of Abandonment states all of the elements required under the Civil Code, so I suggest you look at the Code for the proper format for the Notice!

You need to serve a noticeable leaf of abandonment after the rent is past due the statutory period of time, and then wait the statutory period of time after serving the notice, before you can avoid any liability for taking possession.

Probably, since it appears that your place has been abandoned.