The main reasons traveling alone in a SHTF scenerio is bad has nothing to do with coming across hostiles... how safe will you truly be while sleeping or doing #2?
If you are alone (and armed) and you come across an unarmed group, odds are they won't screw with you. Chances are, they make ask if you want in...
But yes, having a group that you can trust BEFORE Doomsday is the best option.
Insert witty comment here......
Vincit Omnia Veritas
Vincere est Vivere