I live in a country almost the same as mexico ,With even dumber routers and more stranger xD
what u wanna do is get the recommended build (craftbukkit.jar) from
www.wiki.bukkit.org
Then the site will guide you till the point which you can start the server,but no one can join.
what you will do is,stop the server by typing stop into the console,then open server.properties which should be in the directory the server runs from,you will find the properties of your server.
Change the online-mode=true to online-mode=false (if u want it cracked)
Then in the server-ip= space,you will write the ip of your computer,
www.whatsmyip.com then put it in this space.
when you start up the server again,It might say cannot bind to port,that's because the port 25565 isnt forwarded,stop the server,try another port in the server.properties,then try again,hopefully it ,might work from the first try

Hope this helped,