To do this go to Home > dashboard > quicklinks. In the wild card search enter something like this:
@profile_name ^2*|^r* @country "new zealand" @region "south island" @county marlborough
This searches for all cache owners that start with a 2 or an R in the in the given country/region/county. Note the use of quotes surrounding components that have spaces. The ^ can be found above the 6 on a qwerty keyboard, and the | (pipe) is above the enter key. The | can be used anywhere, so you could have @county malborough|canterbury if you wished, which means marlborough or canterbury.
Note that you may want to use the field @placed_by instead of @profile_name, depending on what the challenge requires.
At the bottom of the resulting table you can present the caches on a map to help you choose which to target.