El Monte is right next to the Rio Hondo Bike path. From there you can ride all the way to the coast if you wish. Flabob is across the river from the Santa Ana river trail. That goes to Corona to the west and San Bernardino to the east. Catalina has trails or you can ride into town on the "paved" road. Long climb back up though. Bracket is across the street from Bonelli park which has dirt trails. Santa Barbara has a bike path close by. It's 3 miles from Santa Monica airport to the boardwalk. From there you can ride all the way to Redondo Beach almost exclusively on bike paths. Santa Monica is my favorite because I like to ride to Venice beach and people watch.
One of these days I'm going to organize a Bike/Fly in.