You will see most of the characters throughout the park. But not "all together" in their group. For example.... you might see Mickey, but not Minnie etc.
The princesses tend not to walk around, from what I remember. But I was there 8 years ago!!!!
One breakfast at our hotel, some characters just seemed to "show up" and I THOUGHT that's what the character dining experience was and I was pretty disappointed..... However, my mom had paid for the Cinderella Dinner, so we ended up going to that. IT WAS AMAZING. The Godmother met us at the door and did a photo - then she talked to my daughter and found out all about her trip - like spent probably 5 minutes just with her. My daughter mentioned that she was REALLY afraid of animals in the costumes (I know, yes.... we were at disneyworld with a child afraid of characters!!!!!) And the Godmother said "well, get Charming to protect you from the mice". Then she waved a wand and sprinkled some glitter and told my daughter she would be "protected" until we got back home.
THEN she walked us in and went over to Prince Charming and told him to tell the mice to stay away from my daughter. So he made a big show of going to tell the mice to stay away. And they did (I guess it's not that uncommon for kids to be afraid of the animals). She also got to talk to Cinderella (another photo) as well as Prince Charming. It was absolutely the neatest experience we had at the park, by far.
So - although you might see the mice walking around in the park, for example.... you wouldn't see them ALL TOGETHER in character all at once and talking to the kids. I can't speak highly enough about the experience.
Have fun!