Do you have too build your army with all hand-weapons or all spears depending on how you are going to run them or does it not matter, because some of my saurus have spears and others have HW.
In a private game you do whatever you like, just let your opponent know what weapon they have in advance. In many tournaments they require you to have the model equipped the way it says in the army list. Even in what you see is what you get (WYSIWYG) tourneys you can still mix them, so long as a majority have the appropriate equipment, and it isn't confusing to the opponent.