I see what you mean, again I partially agree. I still think that there
will be a combination of radio/laser/etc signals. and interstellar
probes.

Here's the perfect analogy of what I'm suggesting;

When trying to find other people who like to read books that interest
you, if you go to a library or even on-line, the chances are extremely
higher to finding that person than, let's say, going door to door.

You mentioned on one of my other post's how gamma radiation wouldn't
be used as a communication method, which I agree on. What I was
implying was that gamma radiation could be sign of either antimatter or
fusion type drive, the only two types of energy sources that are
powerful enough for interstellar travel. Again all of this is based on
what we know today, an advanced civilisation probably would have come
up with several new tricks that we aren't aware of, but those I can
only guess at and aren't good to base a hypothesis on.
If we can detect gamma radiation in the terrawatt level circling
several AU's from a black hole this could be a sign of something. (of
course detecting something like that so close to an object that emits
exawatts of energy would be a technical challenge, but thats another
story)
Also if a probe is in orbit, maybe a polar orbit around a black hole,
the blind spot you mentioned wouldn't be a problem.

Thanks guys you've made this discussion very interesting and helped
clairify alot.