In Texas is a landlord/property manager legally responsible to clean the property before you move in?

Not that I know of, and I've lived in Texas most of my life.

Nope, it is a courtesy, at least when I worked in property management it was.

You need to make sure the property is in acceptable condition before you sign the lease.. or add a contingency to the lease that says how long the landlord has to make it right.

Most definately., unless you had an agreement with the landlord to clean it yourself for discount on rent etc...I used to clean apartments for free rent.

They're legally required to change the locks between tennants, not clean it. Even if they do, I recommend that you clean and disinfect before you move in.

Legally... NO.. but I cannot believe a landlord/property manager would have the audacity to not clean up a property prior to moving in.. If I was renting a place.. I would have that in the contract PRIOR to actual signing.. If you did not do that and moved in anyway.. make sure you take pictures of the place.. all scratches, damages, etc when you move in.. pictures you take will have the dates on them.. The first thing I would think of ... if a landlord did not clean up and a TENANT signed the lease anyway is that they want to STIFF you of what he would call damages when you move out.. Be very careful !!