If you go down Irvine, and then turn on University (towards the bay) there is like a nature center that you can go in, and there is outdoor paths.

ALSO… i find this to be the best park of the back bay, if you go on the pacific coast highway, then turn on Jamboree (going inland) then take a left onto Back Bay dr., well it is a great drive, it hugs the backbay all the way to the fletcher jones dealer.