Better way to drop voltage for LED load is to use zener diode. Parallel a specific rating zener diode to your LED array to get constant 6Vdc. Series the whole circuit with an appropriate power rating resistor to limit the total current flow as well as the inrush current. LM317 regulator may be overkill in this application (driving LEDs). Moreover, it will consumes same amount of power as your load is consuming.