From an earlier thread about grill locations adjacent to HGVC HHV:
The BBQ's are public, so they are first come first serve to everybody. Locals use it all the time and there is no time limit for use. The many times I have gone to the Hale Koa, to use the pool, especially in the weekends, will come early in the morning and have a family outing all day, claiming the charcoal grill the whole time. Sometimes a couple of grills depending on how big the group is.
The location of the BBQ grill is behind the Hale Koa, between the hotel and the beach.