The guys at TakeOver LA - http://takeoverla.blogspot.com/ are putting on an Alleycat on April 17th called what else? The Takeover. It sounds like a proper Alleycat and will consist of 5 check points all over LA starting at Orange 20 Bikes - http://orange20bikes.com/.
We won't be there but we've donated some tires and our new Track and BMX grips as prizes for the event. Should be fun!