You can entirely get into Diagon Alley without a working wand -- Hagrid and Harry both managed in book one, on their first trip there. Hagrid's wand had been snapped and he was using wand bits hidden in his umbrella, and Harry had none. (Or, if you're using main force, you just blow a damn hole in the wall.)
Not to mention that its entirely possible for a squib to own a residence on the Floo network, witness Arabella Figg. One cooperative person like such and bam, you can go anywhere in the Wizarding World with an open floo.
As far as being 'hexed on sight', squibs do not walk around with giant signs saying "I AM A SQUIB". Provided that they are not personally known to their audience (as Filch is around Hogwarts), they're just more strangers passing by.
Not to mention that its entirely possible for a squib to own a residence on the Floo network, witness Arabella Figg. One cooperative person like such and bam, you can go anywhere in the Wizarding World with an open floo.
As far as being 'hexed on sight', squibs do not walk around with giant signs saying "I AM A SQUIB". Provided that they are not personally known to their audience (as Filch is around Hogwarts), they're just more strangers passing by.