Install Squid on FBSD with different configure options?

[Ed Flecko]

Hi folks,
I want to install squid from the ports package (i.e.,
/usr/ports/www/squid) instead of installing from source (which, it's
my understanding, would force me to create a squid user, squid group,
etc. manually).

However, I want squid to be installed with the ability to restrict end
users internet access based upon their PCs MAC address, which means I
need the --enable-arp-acl option when installing squid.

I have modified the Makefile (/usr/ports/www/squid/Makefile) to
include this option, but now I'm a little confused - if I use the
standard pkg_add squid command, won't that just fetch the package from
the internet?

How do I install squid from the ports package that's on my hard drive?

I am correct in that when I install the package from my local hard
drive, it will automatically create the necessary users/groups for me,
right?

Thank you,
Ed