I just finished up a search and tour of several in the area. You will be hard-pressed to find one nearby that does not take a self-directed approach to play and learning which is the Montessori-style. (I was looking for one that more closely mimics the classroom setting you'd find in Kindergarten and didn't have too much luck.) With that said, I decided to go with <a href="http://www.goodshepherdpreschool.com/">Good Shepherd Preschool.</a> My choice is based on the needs of a part-time schedule, so if you are looking for full-time you might have a different take. I enjoyed the school's campus and facilities. It appears clean, well-maintained, and safe. They do not allow more than one class per playground at a time so that they can keep a good eye on the kids which I really liked. The play equipment looks brand new and is inspected frequently. The prices are reasonable. The teachers seem very on-the-ball. (They even wear waist-aprons at all times stocked with alcohol wipes, band-aids, etc. for first-aid care.) Even though in theory it is self-directed, when I was in the classrooms I saw the kids sitting in their little chairs at the tables doing a project and staying on task. (They do not receive homework assignments, though, but they give you suggestions for things to do.) It is centrally-located in the middle of Irvine. They do not create long waiting lists. You register right before the year starts, so no worries about it already being "full" (except maybe this time of year when we're halfway into it? I don't know.) You do not have to be a member of that or any church to enroll.
Anyway, hope this helps. I checked some preschools from Tustin to Mission Viejo so let me know if you need any help with something specific and I can look back in my notes. Good luck!