Right hand signals make a lot more sense on a bicycle, and they are legal in California


California Vehicle Code 22111. All required signals given by hand and arm shall be given
from the left side of a vehicle in the following manner:
(a) Left turn--hand and arm extended horizontally beyond the side
of the vehicle.
(b) Right turn--hand and arm extended upward beyond the side of
the vehicle, except that a bicyclist may extend the right hand and
arm horizontally to the right side of the bicycle.
(c) Stop or sudden decrease of speed signal--hand and arm extended
downward beyond the side of the vehicle.