One of the joys of
Disneyland is that you can find the characters all over the park. While they do have some specific meet and greet locations ala WDW, you can also quite often find characters wandering about Main Street or in front of the Mickey floral by the park entrance.
You can also find characters in the Hollywood Pictures Backlot and near the front entrance of DCA. Most of the Pixar characters are found there, but Mickey and friends show up there quite often. On rare occasion, you can find a princess over there too.