Postgres-XL Documentations and also overview describes load balancing as a distinct part of the system.
Am I correct and it is up to Postgres-XL users to load balance or is there specific a way of doing load balance (using load information of coordinators etc.) operation and making it high available?
Postgres-XL does not have HA features. You can put a load balancer in front of the coordinator nodes so they will have redundancy on that part. The nodes have no fail over support though so the loss on any one node anywhere will cause the entire cluster to fail. You can setup mirror nodes but even with that it will require manual intervention if a node fails, and that obviously doubles the amount of hardware you need.