Check again Fin.

I have left my toons skill caped at 375 and even below that and the moment they hit 80 the Cata zones pop open for them. Now it has been a month or so since I last leveled a toon (maxed out at 10 toons on my fav server) but that was how it happened for me on the 5 or 6 toons I did with archeology. It may have taken a few digs before a Cata site showed up but regardless of my skill level my toons were getting their ass handed to them in Twilight Highlands at 80. Of course they were still wearing level 60 gear but I wasn't wasting gold on gear upgrades past basic greens until they hit 85. Regardless, I still would have switched over to Outlands and Northrend for a while at some point just to get the different rares these zones offered along with the acheivements that go with it.
I am not certain about Teveel's post about Archbot initially learning Archeology for you. I have always just gone and learned the skill by hand and then started the bot right from the training area in SW. It may be correct that the bot will learn the skill for you at the begining. Easiest way to check is just to start the bot and see what happens.