Joseph,
You are totally missing the point, almost all cities including Jerusalem have no status of an עיר’ as far as Minhag goes. Kiryas Joel might have such status as there is one Bes Din and one Rav that was accepted via it’s residents.
Also, doing or refraining from something by many individuals does not establish something as a Minhag haMakom. It has to officially established and accepted as a Minhag of the city.
I don’t think merely passing a city is either a condition to מחייב one to follow it’s customs. You have to at least live there temporarily to be included in the the Minhag hamkom Chiyuv, however it all depends when and what and how the minhag was implemented in the first place. Was is it an official tekanah on all people of the town before and after? Was it that each individual happened to follow certain customs and poskim?
In any case, most of your comments indicate that you are speaking without having any knowledge on the subject, which is complex. If you want to have any say in the matter, you should learn trough most of the Pri Chadash I mentioned earlier.