I've done it 2 or 3 times there. Each time I've been there, there was at least one or more other singles as well. It's a nice way to start the morning!
I did it solo and got a beautiful window seat looking out over Fantasyland. I loved it. It's too expensive for me to do it again anytime soon, but I am so glad that I did it once! No one paid any attention to me solo, but the princesses kept asking if I wanted to be in the pictures with them. I didn't mind not being in them, but maybe next time!
I had lunch at CRT solo back in December (see trip report). I had a good time and had a lovely seat by the window. The characters were very nice, food ok, service, good and thankfully, a very ncie family next to me who took photos.
But if you don't want photos, you can just talk to them or just wave hi. For the most part, I tihnk the characters, especially face ones, like it when adults only show up. They get to play along a bit more.