Try specifying a region for the ec2 module.

playbooks/el6_temp_instance.yml

@@ -17,6 +17,7 @@
   - image: "{{ el6_qcow_id }}"
   - instance_type: m1.small
   - security_group: default
+  - region: nova
 
   tasks:
   - include: "{{ tasks }}/transient_cloud.yml"

playbooks/el7_temp_instance.yml

@@ -14,6 +14,7 @@
   - image: "{{ el7_qcow_id }}"
   - instance_type: m1.small
   - security_group: default
+  - region: nova
 
   tasks:
   - include: "{{ tasks }}/transient_cloud.yml"

playbooks/f19_temp_instance.yml

@@ -14,6 +14,7 @@
   - image: "{{ f19_qcow_id }}"
   - instance_type: m1.small
   - security_group: default
+  - region: nova
 
   tasks:
   - include: "{{ tasks }}/transient_cloud.yml"

playbooks/f20_temp_instance.yml

@@ -14,6 +14,7 @@
   - image: "{{ f20_qcow_id }}"
   - instance_type: m1.small
   - security_group: default
+  - region: nova
 
   tasks:
   - include: "{{ tasks }}/transient_cloud.yml"

playbooks/fedora_temp_instance.yml

@@ -14,6 +14,7 @@
   - image: "{{ f18_qcow_id }}"
   - instance_type: m1.small
   - security_group: default
+  - region: nova
 
   tasks:
   - include: "{{ tasks }}/transient_cloud.yml"

tasks/persistent_cloud.yml

@@ -5,7 +5,7 @@
   ignore_errors: true
 
 - name: spin it up
-  local_action: ec2 keypair={{ keypair }} image={{ image }} type={{ instance_type }} wait=true group={{ security_group }} ec2_access_key={{ persist_access_key }} ec2_secret_key={{ persist_secret_key }} ec2_url={{ os_ec2_url }}
+  local_action: ec2 keypair={{ keypair }} image={{ image }} type={{ instance_type }} wait=true group={{ security_group }} ec2_access_key={{ persist_access_key }} ec2_secret_key={{ persist_secret_key }} ec2_url={{ os_ec2_url }} region={{ region }}
   register: inst_res
   when: host_is_up|failed
 

tasks/transient_cloud.yml

@@ -1,6 +1,6 @@
 ---
 - name: spin it up
-  local_action: ec2 keypair={{ keypair }} image={{ image }} type={{ instance_type }} wait=true group={{ security_group }} ec2_access_key={{ transient_access_key }} ec2_secret_key={{ transient_secret_key }} ec2_url={{ os_ec2_url }}
+  local_action: ec2 keypair={{ keypair }} image={{ image }} type={{ instance_type }} wait=true group={{ security_group }} ec2_access_key={{ transient_access_key }} ec2_secret_key={{ transient_secret_key }} ec2_url={{ os_ec2_url }} region={{ region }}
   register: inst_res
 
 - name: add it to the special group