Fleeing the undead on your own is never recommended, trying to flee or fight alone is almost a death sentence no matter how good you are or think you are. Even though there will always be exceptions that prove the rule a group represents your best chance of surviving the undead and staving off insanity.
When preparing for the undead, food, weapons, and a defensible structure are high on the list, what also needs to be high on the list are other people. The reasons are endless but high on this list is that many sets of hand can take care of situations and projects quicker than one alone.
When preparing to fight, live, and survive as a group there are several considerations:
Compatibility: While these people may not be love interests if the members of your group often get on your nerves for any reason then they may not be the best choice. The undead will take a toll on you, no need for your companions to also grate your nerves. Again this is when you are preparing, when the undead rise you may have no choice, however, if you are able to choose your compatriots choose wisely. Not only with you have to rely on these peoples skills but their mental toughness, if they are either mentally weak or unstable then perhaps you may need to reconsider.
Specialties: Having each member of your group specialize in one of two jobs such as scouting, map reading, carpentry, medicine, hunting and fish, engineering, and not just for cars but to build fortifications and traps, language(especially if you may have to venture to another country where you do not share the language, for example our European brethren.), weapon smith, and numerous others can be a priceless in times of need. Also crossing training each other with the things you have learned also helps when one member may no longer be able to perform their job.
Safety: Ignoring the possibility of Tom going postal because from the stress there is safety in numbers. Not just because of moral support and the ability of being able to sleep with the knowledge there is someone pulling guard duty, but the knowledge that if you are injured there is at least the possibility that you will be saved and be able to fight another day, unless of course your group members are cowards and leave you for the dead.
Supplies: While a group will consume a larger quantity of food and water a group can carry more weapons, and gear. A trade off that will often outweigh the disadvantage since you may be able to carry less or be able to carry other thing since others in the group already posses thing on the MZPK. Also while there may be less food to go around for those who are willing, when times get especially tough other group members may provide nourishment.
Battle Buddy: The greatest consideration that you must face is whether or not you trust the man or woman next to you. They will be watching your back, fighting by your side, giving the zombies someone else to try to devour, and possible stopping you from going insane, as well as stopping from becoming a zed head if the worst happens. If you doubt that person then you cannot focus on the most important job, staying alive.