Yes, walking with another confident dog should help him. It is all new to him and he will see how the other dog ignores traffic and such.
And to get him more used to people, I would get some pieces of cooked chicken or sliced lunch meat and get some strangers (maybe your friends that the dog does not know) to feed him small pieces so he associates new people with good things and special treats. Keep the meetings with new folks sweet and short at first and see how he does.
As others have said it will take time but he should come around. Many dogs are shy when taken off their home yard but most will come around. Shyness can be genetic and also be influenced by early rearing.