For 802.11b speeds (1, 2, 5.5, 11), the answer is yes. ALL management frames are sent at 1Mbit/sec to insure that all radios hear these frames. However, 802.11a/g management frames are sent at the connection speed. All are unencrypted. When 802.11w gets approved, these frames will also be encrypted.
Go to the source. IEEE 802.11 specs at:
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This looks like a good start:
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