Is changing how the game is hosted even an option ? I haven't seen anything related to this on the SC forums. Right now any multiplayer game I joins lags out and I get dropped right away..but the games do at connect at least, they are just unusably laggy.
The cause of the poor performance for Starcraft 2 is that the residence networks, and wireless, are setup so no device can be a server, it will not allow any incoming traffic. If you are able to change the setting from hosting the game on your local computer to host the game on battle.net it may resolve the problem.
Let us know if you have any questions.
Technical Support Representative