Not a good way of doing it. First, the NPNs are sinking ~0.6A, so they will need a base current of ~60mA, which the uC cannot source. Also, the Dissipation in the LM317s will be huge; they will need to be on huge heatsinks...
I would use an NFET for the switch. By moving the current-limiting resistor into the source, the NFET can do double-duty by limiting the LED current at the same time.
What is the Vdd for the uC? What is the forward voltage for the LEDs at 0.6A? At 0.3A?