I ride up Lake Avenue in Pasadena on a 49 x 16 without too much trouble - and then up and down the hills and across to the Rose Bowl - Griffith Park shouldn't be too bad depending on which road you ride.
Hijack (sorry) - Now that I am back on the saddle (had a bad spill a few months back and have been too busy helping with my wedding and soon-to-be-wife's new business - never do this two things at the same time) - I will have some more time to get around in addition to my 3 mile r.t. ride to work and occasional ride.
I know a few other riders who have just moved into the area who are also looking to meet up with others. I will not be available until early October, but maybe a meet up at Lucky Baldwin's or other such fine establishment and then head out.