Very true sir in a small fraction of cases, see http://www.umsl.edu/~renners/Ming_etal_Sex_chromosomes_2011....
(well, if you wanted to be precise, you could have said "there are more sex determination systems in the world than just XX/XY", since these letters only make sense when it comes to comparing different systems, sex loci relate to one chromosome within the same species)
In this particular case however, it's not true, Cycads are in the XY/XX system, see http://aob.oxfordjournals.org/content/26/2/261
So we may proceed and clone those females :)