In my experience Mexico is very slow to respond, and you won't get any of the things that other VOs send out (eg AOR2, pre-arrival services, etc) until they're actually nearly done. Then things will come in over a couple months. YMMV.
What's frustrating is that the medical exam gets requested up front in so many cases, but then the BGC and everything else takes forever. They should really be asking for medicals 6 or 9 months in so that they don't expire before the application process completes.