How to talk to the team on Left 4 Dead 2

Valve removed the vocalization commands to stop people spamming in multiplayer games, all that is left are the speech wheel that come up when you press z or x (using default controls).

Edit: This is the very hacky way of doing it through the radial commands which may or may not work.

The safest place, by definition is the safe room.

Other safe places are rooms with doors closed, of course until infected destroy them. And in general all places that can have only few entrances (one or two) so that they can be easily guarded by your team mates. Trucks, garages, rooms and so on.

If you are instead searching places where infected cannot reach you, they probably go under definition of maps bugs/exploits. Because for sure map designer/developers do not want to add places where you can safely stay without being reached by infected.