The street is what I favor unless there is a reason that the street is especially unsafe. The only place I have used sidewalks is for a few block stretches in Clearwater, Florida where the bike lane disappeared and the street was busy with crazy Florida drivers. Clearwater did not have many back streets that went through to where you wanted to go. It probably is the worst place I have ever ridden a bicycle despite the fact that it had a couple of lovely bike paths. It was illegal but I did it anyway because it was the only somewhat safe thing to do. Or I took the bus. Which I also did quite a bit to get to bike paths.