Disclaimer: I am NOT a ski professional, so please process my comments accordingly.
The skis themselves should be "safe," although they are not ideal for learning.
The bindings, on the other hand, should, as always, be tested with your actual boots by a qualified technician, before being used.
This is a ski that, as I recall, is approaching the 10 year old mark, so, it doesn't represent the latest and greatest technology. However, it was a well-regarded ski in its day. I skied the little brother - the SX 9 - and it was excellent. If it has not had too hard a life, and has a good tune from a good shop, and you are skiing mostly on groomed trails, the SX 11 should be passable. When you have the ski tuned, advise them that you are a beginner. They may want do dull the very ends of the ski slightly with a gummy stone, to make it less "grabby"; because it's a fairly stiff and demanding ski, this may make it a bit more error-tolerant. Ideally you would be on a ski that was a bit wider and a bit more forgiving of mistakes, especially if you are on the lighter side (you did not provide your weight). Note that this ski will not do you any favors if you venture off piste. Generally it's not a good idea to make your equipment choices based on what a friend happens to have lying around in his basement. You will probably be spending a fair amount of your precious time and money on your ski outings, so settling for marginally appropriate gear is a false economy.
Hope that helps.