As far as radio signals, like those picked up by SETI, I don't know, maybe they were on the wrong frequency. Maybe they were not transmitting on an audible frequency. Yes, I believe aliens are among us now. I know the crop circle situation, and I don't really know what to make of them. I think some of them are real, and some are made by humans.
Humans can do something really similar.
In my personal opinion, based on no facts, I believe some of them are for real, and some of them are fakes. I think the pyramids in Egypt and some in Central America are examples of a lot of very, very advanced technology, and I think it's very likely that that technology came from extraterrestrial sources. I really don't have too much opinion on that. I think that if we learn to become peaceful in this world, and stop all the warfare among nations, it might be a good start to encourage appearances by extraterrestrials. I think both.