There probably is no life anywhere in the Solar system except earth. For starters, liquid water appears to exist in very few, if any, places in this system. But this situation would exist even if the Milky Way was crawling with biospheres. And we still don't have the technology to detect biological activity on earthlike planets even around the nearest stars.

What we can detect, though, suggests life is common in the Galaxy: Planets are common, the existence of abundant pre-biotic chemistry, all the way to amino acids, is a well known, and the ubiquity of sunlike stars is established. Most important, the variety of hostile environments in which life exists on our own planet, and its ability to survive in a dormant form even in deep space, gives us strong circumstantial evidence for the existence of extra-terrestrial life. My guess is single-celled life is probably abundant, multi-cellular creatures much less so, but I can't quantify it any better than that.

On the other hand, I am very pessimistic about the odds for intelligent life. We are probably only one of a few, perhaps the only one in our Galaxy, perhaps throughout its entire history. And the more I think about it, the more pessimistic I seem to get. I too, hope I am mistaken about this, and I take some comfort in considering my opinions about intelligence even less based on hard evidence than the ones on life.

I'm sure once we learn the answers to these questions, whatever they are, we'll all simultaneously slap our foreheads and say "Yeah, it's obvious, we should have seen that all along."