Yes is the short answer. Make sure you have villain chat enabled in options so you can read what the villains reply with 
Those that have enabled hero/villain chat will be able to see it. However as it is automatically set to disabled (and the fact many people are not even aware of it) many people would probably not see the broadcast.
Heros
Max Powerz: Lv 50 Tanker
Villains
Max Khaos: Lv 50
Overlord of E.V.I.L.
My Brute - http://maxy-khaos.mybrute.com/
LF SG! Arc ID# 193083
On the bright side, most PVP regulars have the enemy chat enabled, so if you really feel the need to congratulate someone (or speak to them), you could try asking a regular to pass on the message or get them to enable PM's briefly.
Hi guys,
random question - If I send something on the 'broadcast' tab - in a pvp zone do both the heroes and the villains get to read it? ( I play CoV)
cheers y'all