Apple have moved their database of WiFi hotspot locations from a commercial server to one of their own recently. Unless the hotspot where you are staying has been entered into the Apple database - either intentionally by the owners (unlikely) - or unintentionally, by someone using a GPS-enabled iPad or iPhone in the vicinity of that WiFi hotspot (more likely) you'll be unable to retrieve your position.
The radio frequency circuitry used by GPS and 3G is very similar, so it's incorporated into the same chipset in the iPad - which is the 3G chipset - thus meaning no GPS for WiFi iPads.
Tim