The solar cell won't be able to respond fast enough. You want to use a photodiode / phototransistor for that.
Also, I don't really like that circuit you're using. The AC power in the laser beam (the useful part of your signal) still has to come through the transformer, the LEDs across the secondary will introduce horrible distortion, and the DC current in the transformer secondary will probably saturate the core. All you really have to do is feed the laser diode from the collector of a transistor, and either run the transistor in class-A (straight audio), or PCM (digital audio).