Once my father was diagnosed with Alzheimers, we began the search for retirement homes and assisted living centers. A hospital social worker was very helpful in providing lists of centers that catered specifically to dementia and Alzheimer's care, so we were able to visit them. The problem you will encounter is simple: the cost. It's shocking. I mean, really shocking. To house my dad comfortably in a senior living center near-ish to my mom's house would've cost about a million dollars. No, that's not hyperbole. To sign the contract to get him in as a resident was just shy of a million. And Dad, being paranoid in his dementia, had secretly cancelled his long-term care insurance. Luckily, it turned out that Dad may NOT have Alzheimer's after all, as he has actually improved; he might just have had bouts of acute dementia following some mini-strokes after a bypass.
In short, in my area, we found several nice homes but the cost is severely prohibitive. Thank God, Mom has been able to earmark money over the last few years to get him into that care-home someday if need be, but they're lucky to have a 6 figure pension.
If you find a place, you will most definitely have to tour it first, consult reviews and family members of residents (if possible). And definitely read the contract carefully. The costs are truly staggering.