Your wireless access point would not be blocking traffic. (Unless it's a reconfigured router that you set up and forgot to turn off the firewall. If this were the case, you'd know.)
Wireless access points are basically unintelligent switches. They don't pay any attention to what passes through them.
Are you attempting to forward the port with UPnP or manually? Have you tried connecting to your server's local IP address from another computer on the network? (On Windows, type "ipconfig" in a command prompt to quickly get your IP address.)
If local streaming is working, you need to check if the port is forwarded. Go
to You Get Signal and change the port to your Subsonic port. (It automatically detects your Internet IP. If the port is closed, then you've got a port forwarding issue at your router most likely.
Another possibility is that some ISPs (Verizon I know is one of them) block port 80 and a few others. Try running Subsonic on some other port like 8080 or 4040 if you believe the port is forwarded correctly and it happens to be port 80.
If you need any further assistance, I would be glad to help you.
Cheers,
Kirk