A local installation of Squid is a really good idea if you have limited bandwidth. You can set the maximum_object_size of Squid to a large value and tell it to be very aggressive in caching .deb files (which should never change so you can override all the cache settings to store them for a long time - disk is cheap).
If the reason for installing Squid is for caching deb's then you'll be much better off with apt-cacher. Even if you want squid as a general caching solution, you'll still be better off using apt-cacher for your deb's. The reason it's better than squid is that it's smart enough to know that packages are the same packages even if you get them from different mirrors, so if you use a nearby mirror and it goes down and you have to use another, apt-cacher will still be smart enough to know if it already has a copy of some package even if it wasn't downloaded from that mirror originally. It can also intelligently discard obsolete packages (or not, if it's useful to you to have old packages kept around for whatever reason). Finally, if something broke, the packages are stored in /var/cache/apt-cacher so you can go and get them manually if required. James