It's been a while since we were there, but the last time we went, the daily schedule had SOME info about character meetings. Not the map, but the printed sheet of paper (usually colored paper) with all the show times and parade times. Keep in mind, though, that some characters appear only in California Adventure, and some only in Disneyland. (Some will be at both.)
If you get there before opening, you MIGHT get to see a character or two out on the central plaza between the two parks. We caught Donald Duck once that way.
I think the only way to see Mickey Mouse is to wait in the long (LONG) line at his house in ToonTown. Same with Minnie Mouse. She has her own separate house.
I would expect very large crowds tomorrow. A few school districts are back in session this week, but most are not. And August is a huge month for European tourists (though they seem to prefer the national parks).
DS '04 "Boogaboo"
DD '08 "Lilybear"