Apple hasn't announced an exact date for iPad availability. Rather, their website still just says "late March" for wi-fi only iPads. There's also no date listed for pre-orders, but that may be about to change, as well.
AppAdvice says an anonymous source "familiar with the matter," told them that Apple will begin taking pre-orders of the iPad as early as February 25th. Of course, you can stamp this note with a big fat "rumor," and as such, who knows, really?
There's also really no reason to hang out on Apple's site refreshing, or to turn on auto-refresh of a tab dedicated to http://www.apple.com/ipad
. You can simply sign up on that same page to be auto-notified when pre-orders start.