I use Andchat and IRC works just fine on my droid. I connect to port 6667 and 7000 and hell I use IRC on home with verizon DSL and have no problems with it. What servers are you trying to connect to? I use Undernet and everything seems to be fine there.
EDIT: I am also able to use it on 3G or WiFi
Is anyone else irritated that Verizon blocks IRC traffic? It's not like I need to use IRC, I'm just bothered that I'm not allowed to.