I'm working with Pedro to pass his TDI currently. It'll be a long road, as he just LOOOOVES people so much he can't stand sitting still until they get to him. Same for other dogs. He's young and still learning, but we'll get there one day.
Some things I'm doing now, under guidance of my mom who has 3 TDI dogs and is getting ready to test 4 and 5. Pedro and I tag along with her to the assisted living facility where she works. We got the ok from the director and I am picky about who we visit with at this point. He's been making short visits since he was 12 weeks old. Walkers, canes, o2 tanks, wheelchairs and weird moving people don't fluster him at all since he's so used to them. It really is the biggest challenge in all of this I think. If you've got an assisted living facility, and you trust your dog in public in general, you might ask if they'd mind a visit. You don't *have* to be TDI or Delta certified to visit if the facility ok's it. (ETA: TDI insures you as part of your dues to them. If you aren't certified, you're on your own if the dog bites or hurts someone.)
Also, if you've got friends or family in a nursing home/assisted living facility/long term care situation, ask the supervisors if you can bring your dog to visit that specific person. This often works out easier than just randomly picking people to visit. When my dad was in the hospital we took Pedro and one of my mom's dogs to visit with him. The hospital didn't mind a bit as long as we were only visiting my dad. They did ask if he was current on shots/worming and I offered to bring vet records which they declined.
Be prepared if you go visiting to get a wide range of reactions. LOTS of folks think it is absurd that dogs are in a medical facility and are quite vocal about it. Some people are scared, some people think they are too "good" to pat the dogs, and the most fun ones are the ones who light up like a Christmas tree at the sight of the dog. People do get very attached to your dog as well. More than once Mom has had dogs invited to visitations and funerals. Seeing the power a dog has to give comfort in those situations is beyond amazing.
One last thought and my novel is done
See if you can find a mentor/partner and tag along sometime. Leave your dog home and just watch that dog work. Really feel it out to see if *you* will be comfortable with sick/hurting/frail/developmentally disabled people in a facility environment. It can be overwhelming at times. I prefer the old but not bed bound people and the developmentally disabled adults. That is where *I* am most comfortable. I felt bad about this for a while, thinking I should be ok with anyone. I'm not, and I have to know my own limitations. Forcing myself, and being uncomfortable, was doing Pedro a disservice. He couldn't focus when I wasn't at ease.