There is an exit off the 241 toll road. You can reach the 241 from the 405 or 5 down by the Irvine Spectrum. Go to mapquest.com and punch in Irvine lake recreational area. and it should bring up some directions to there. Good luck
On mapquest.com Type in Irvine, CA Map will come up Find where the 261 and 241 freeways meet. There will be a city called Cowan Heights and its just below it. You will see a small lake just to the right. Click on the lake. Them zoom in.