Yes.  USB 3.0 devices
are compatible with USB 2.0 ports.  The maximum read/write throughput of
USB 3.0 flash drives will be limited to the maximum available bandwidth on your
USB 2.0 ports, however they will recognize and function properly in those
ports.
Likewise, if you have a
computer equipped with USB 3.0 ports and connect a USB 2.0 device, the device
will be recognized and operate to the maximum capability of that device
when connected to a USB 3.0 port.