I grew up in Irvine and just moved back here last summer after 14 years in LA. I LOVE it. One of the greatest things about Irvine is you are almost always within walking distance of a park (or 2 or 3) and you can usually walk to the elementary school as well.
If you want an older neighborhood, with bigger yards (relatively speaking) and no mello roos, check out Northwood. The houses are nice - mostly built in the late 1970's - and the schools are great. We go to different parks all the time. Turtle Rock and Woodbridge are also good if you want older neighborhoods; Turtle Rock is the most expensive of these. The schools up there are the best in the city (among the best in the state), but not all of the houses are walking distance from the park and schools.
If you want a newer neighborhood, I think Northwood Pointe is the best, followed by Woodbury. If I could have afforded it, we probably would have moved to Northwood Pointe.
We are in Northwood and are extremely happy. Feel free to send me a private message if you want more info about specific schools or neighborhoods.
***One more thing I want to add - there are a few neighborhoods in Irvine that are really nice, but are actually in the Tustin school district. So if you're moving here for the schools, keep that in mind about certain neighborhoods. Northpark, Northpark Square, Orchard Hills, & West Irvine are all TUSD. The schools are good, but don't have the reputation of Irvine schools.
K.
http://oc.citymommy.com