Discuss and learn French: French vocabulary, French grammar, French culture etc.
You can say Ne pas ouvrir avant la fin des des discours (s'il vous plait).
I'm not sure having seen s'il vous plait written at the end of this kind of phrase. It's correct but not really usual
Or I suppose "avant le début des discours" if that was what was intended.
I agree I don't think you need to add "s''il vous plaît" which is a bit long-winded. If you want to see it this way, using the infinitive "Ne pas ouvrir..." rather than "N'ouvrez pas..." is enough of a "marker of politeness" to be roughly equivalent of the "Please" in English.