You want players to have their view sideways?!
public Event_OnPlayerSpawn(Handle:event, const String:name, bool:dontBroadcast)
new client = GetClientOfUserId(GetEventInt(event, "userid"));
flAngles = 90.0;
TeleportEntity(client, NULL_VECTOR, flAngles, NULL_VECTOR);
That should do it - untested though. It rolls every player's view to the side. Why would you want that?