have you thought of the early learning center through the sabin-schellenberg center. it's in milwaukie on johnson road right near the 205. it is run through north clackamas schools and it is a learning program not only for the kiddos but high school students as well. there are 15 kids per class and one official teacher. then there are 3-6 high school students who are learning to be preschool teachers.
my daughter absolutely loves preschool. this was her first year and i can't begin to say how great she has done. she can write her name, count to 20, knows about 12 letters by sight and knows simple words by sight...mom, dad, cat, dog. and she will be 4 in july. i worked with her on most of this stuff before she started but it's really sticking in her mind since going to school. oh, and did i mention it's $70 a month for three days a week? (great, huh??)
look into it soon if you're interested because there was a wait list last year and i think applications have already been accepted for 2008-09. good luck!