Personally, I went to Outlands when I was 60 or 61... don't remember which. I finished up WPL, EPL, Silithis, Winterspring, all of those old places before hitting the Outlands.

I ding 70 when I finished Nagrand.

Finished Blade's Edge and Netherstorm and now have 2500 gold (AND a regular flying mount) on each of my toons from questing. About to head into SMV soon after finishing up some of the Ogri'la quests.

I would suggest this to make some easy gold from quests. If you hit Outlands right when you hit 58, you'll finish up a lot of the quests and have to rely on dailies for most of your gold for the flying epic.