I am trying to run amcl under a namespace (we'll call it robot_name) for a single turtlebot, in order to eventually use amcl on multiple robots. I run titianbot.launch first:

<launch> 
<arg name="robot_name" default="titianbot"/>

  <group ns="$(arg robot_name)">

    <param name="tf_prefix" value="$(arg robot_name)" />

    <include file="$(find turtlebot_bringup)/launch/minimal.launch"/>

    <param name="mobile_base/base_frame" value="$(arg robot_name)/base_footprint" />
    <param name="mobile_base/odom_frame" value="$(arg robot_name)/odom" />

  </group>
</launch>

Note the parameter changes to include the namespace prefix. I then run titian_amcl.launch

<launch>
  <arg name="robot_name" default="titianbot"/>

  <!-- MAP SERVER -->
  <arg name="map_file" default="$(find map_server)/maps/theoffice.yaml" />
  <node name="map_server" pkg="map_server" type="map_server" args="$(arg map_file)" />
  <param name="frame_id" value="/map" />

  <group ns="$(arg robot_name)"> 

    <arg name="tf_prefix" value="$(arg robot_name)" />
    <param name="tf_prefix" value="$(arg tf_prefix)" />

    <include file="$(find turtlebot_bringup)/launch/3dsensor.launch">
      <arg name="depth_registration" value="false" />
      <arg name="scan_topic" value="/$(arg robot_name)/scan" />
    </include>

    <!-- AMCL NODE -->
    <arg name="initial_pose_x" default="0.0"/> 
    <arg name="initial_pose_y" default="0.0"/> 
    <arg name="initial_pose_a" default="0.0"/>
    <include file="$(find turtlebot_navigation)/launch/includes/amcl.launch.xml">
      <arg name="initial_pose_x" value="$(arg initial_pose_x)"/>
      <arg name="initial_pose_y" value="$(arg initial_pose_y)"/>
      <arg name="initial_pose_a" value="$(arg initial_pose_a)"/>
    </include>

    <param name="amcl/odom_frame_id" value="$(arg tf_prefix)/odom"/>
    <param name="amcl/base_frame_id" value="$(arg tf_prefix)/base_footprint"/>
    <param name="amcl/global_frame_id" value="/map"/>

    <!-- MOVE_BASE NODE -->
    <include file="$(find turtlebot_navigation)/launch/includes/move_base.launch.xml">
      <arg name="odom_topic" value="/$(arg robot_name)/odom"/>
    </include>

    <param name="move_base/global_costmap/robot_base_frame" value="/$(arg robot_name)/base_footprint" />
    <param name="move_base/local_costmap/robot_base_frame" value="/$(arg robot_name)/base_footprint" /> 

  </group>
</launch>

Note the parameter changes to include the tf_prefix namespace. I get the following error repeated every 5 seconds forever:

 [ WARN] [1403220638.626315765]: Waiting on transform from titianbot/base_footprint to map to become available before running costmap, tf error: 

You can see that I attempt to change the relevant parameters to include this "robotname" prefix. When amcldemo is run with no namespace, amcl node publishes on 6 topics, and the map-->odom transform is published, however in this version with the namespace, only 4 topics are published, and the transform from map-->robot_name/odom is not published. So it seems like the amcl node isn't fully initializing, though I don't know why.