Yes, that is the drain below the intake. Not an ideal skimmer drain, but you don't need to drill the skimmer. Drilling the skimmer box would be easy, but it looks like you would need to use weld, or the rubber grommet type fitting "thingies" (technical term) on for the connection to a drain, as I don't know how well you would be able to access the interior for a bulkhead type fitting. And the rubber fittings scare me on an external skimmer, especially with a pump like a dart. Also, even if you only had 1/4" pipe(I think the hole is a bit larger, but maybe not), there's not that much water that would need to drain out, won't take too long.
wizsmaster - have you ordered the skimmer? I really, REALLY like the looks of this skimmer, and would order one, but the setup for my new 250 is nearly complete, and I didn't plan for a skimmer this size, so no idea where I would put it. $#!^