MySQL NDB Cluster settings to prefer data node on localhost than remote
I would recommend that you upgrade to MySQL NDB Cluster 7.5. Then you can take advantage of a new relevant feature:
https://dev.mysql.com/doc/mysql-cluster-excerpt/5.7/en/mysql-cluster-system-variables.html#sysvar_ndb_read_backup

With the read_backup feature used in a setup like yours--with only one node group (shard/partition)--all reads can be done locally at the given data node and no cross data node work is ever required. 

Another related new aspect of this feature is that when it's used, the API node (the mysqld process) will automatically select/use a data node available on localhost as the transaction coordinator.

So this should give you exactly what you're looking for here! I expect the "read backup" feature to be extremely popular with many MySQL NDB Cluster users, especially those with setups similar to yours. :) 

For some additional information:


https://blogs.oracle.com/MySQL/entry/mysql_cluster_7_5_is
http://mikaelronstrom.blogspot.co.uk/2016/10/read-any-replica-in-mysql-cluster-75.html