I found the answer using AudioStreamBasicDescription. All you have to do is:
UInt32 getAudioDataSamplingRate( AudioFileID fileId )
{
AudioStreamBasicDescription bsd;
UInt32 ps = sizeof(AudioStreamBasicDescription) ;
if( AudioFileGetProperty(fileId,
kAudioFilePropertyDataFormat, &ps, &bsd) )
puts( "error retriving af basic description" );
return bsd.mSampleRate ;
}