In and around Pasadena/Glendale.
In answer to the Q about Angeles Crest: the crest is still accessible; only the lower section of ACH is closed. You drive up Big T, go left on Angeles Forest, turn right on Upper Big T, and then connect to the upper section of ACH. Adds about 30 min. to the drive, but the backcountry is open. Great time to get out in the backcountry -- the road closure has WAY reduced the number of folks in the backcountry. I did two hikes along the PCT last month. Hardly saw anyone.
And of course there's always the San Bernardino and San Jacinto Mountains as well as the mountains in Ventura County.
BUNCHES of hikes out there. So Cal is fabulous place for hikers.