I'm putting my wife (68) in a personal care/memory care facility next week. Should I try to get POA before she goes in?

If you can, yes you should. Call aN estate lawyer and get a consult. Dementia does not necessarily mean she is not competent to sign. She needs testamentary capacity. This means she needs to be able to understand, in a lucid moment, the POA meaning and what she is signing. If she has no lucid moments then it’s probably too late.

YES

I got my trust attorney to draw up the paperwork, and a traveling notary came to my house for us and a witness ( neighbor) to sign. I was able to obtain POA, Medical POA, a Will, and Trust documents about six years ago before my Mom was placed in assisted living and then memory care for dementia/ Probable Alzheimer’s. I was her only child she had no spouse and it would have been extremely difficult to take care of her without the documentation in place.

It may be too late for her to assign you as PoA as the others have stated she needs to have enough capacity to fully grasp what it means. You will need to pursue guardianship through the courts, which will allow you the same authority on her behalf. If you don't, the county will, and then they will make all her decisions, not just medical and financial. I wish you all the best

John, are you looking to get Power of Attorney for yourself or for your wife?

If for your wife, only your wife can decide who she wishes to be her Power of Attorney and she would need to be able to understand the legal document. Is she still able to do that being that since she has Alzheimer's/Dementia?

John
A person gives their Power of Attorney to someone they trust to act for them in all the ways the POA spells out. They must be of sound mind when they do so.
The fact that you are putting your wife in a memory care facility next week suggests she is not of sound mind.
But having said that, an attorney would question your wife out of your presence to make sure she understood what she was signing. If he is satisfied she understands that she is asking you to make decisions for her, then it might not be too late.