No. Units with locust WILL NOT be picked in pick all units in area, etc. The only way to include them is to create all units with locust using triggers and add them to a unit group, and whenever you pick all units in range or region, etc. you have to pick that group too.
Units with locust lose all forms of UI. They have no life or mana bars, even if you hold alt. They cannot be select by clicking or box selection, and are not affected by AoE spells. They also cannot be autotargeted by units, and finally cannot be issued an order through triggers or non-triggers. (and cant be force-selected through triggers)
One major fallback with Locust is that if you add it then remove it, the unit that you added it to will remain unselectable by clicking (must box-select) and will lose its mana and health bars overhead.
I usually remove my dummy casters by adding expiration timers to them, it works fine.