Is Asynchronous URLFetch App Engine's fastest way to send real-time messages to external systems?

Question

Is Asynchronous URLFetch the fastest mechanism to get out of the App Engine sandbox?

http://ikaisays.com/2010/06/29/using-asynchronous-urlfetch-on-java-app-engine/

We had experienced very slow URLFetches in the past, but think Pull Queues would introduce too much latency.

Our Google App Engine app needs to send UDP messages in near real-time. Since App Engine supports only HTTP on port 80, we plan to use HTTP POST to EC2/Rackspace instances that in turn send the UDP message.