3 people is a bit of a crowd. You're probably less likely to get rides with that many people.
Yeah, this might be a problem. When I hitchhiked with my friends we always split into pairs and only met at certain points (and obviously at our destination).
Last summer I hitchiked all the way across my country. It was fun, I met some nice people and we didn't really have any major trouble finidng people willing to pick us up. It's still very luck-dependant, though - my friend spent several hours waiting for someone to stop, when I was picked up almost immediately on the same road a while earlier. I noticed it actually helps if you're a girl. People are more willing to trust you, I guess they don't expect you to put a knife to their throats or something

It was fine as long as I was travelling with a male friend - I'm not sure if I'd risk going completely alone.
I never tried hitchiking abroad. One of my friends did, he went to Spain - passed through Germany and France on his way, but I don't know how it went so I can't give you any advice. He didn't get murdered though
