Yes, announce will work no matter what all of the other settings are set to. What build of sourcemod are you running?
With announce turned on, when you spawn it will say "Friendly-Fire is disabled in spawn." And then when you leave the saferoom: if l4d_ff_limit is set to 0 it will say "Friendly-Fire is ON", or if l4d_ff_limit is greater than 0 it will say "Friendly-Fire Limit % HP, griefers may be banned."
Also if you are running a plugin that forces the player join spectator first, it will cause the first announcement "Friendly-Fire is disabled in spawn" to not show up. I will try to fix this in the next version.