Coronado,California. The Navy training base specifically,think about all the awesome obstacle courses and the beach. Also relativley warm. If I can't get to nerf there another place I would like to nerf is right next to Piney. Groove would also be awesome.
Coronado would be... kinda dull. There are a couple of o-courses but they're far apart from one another and not really designed to be fun.
The live-fire ranges aren't designed for someone to be on the other side, firing back.
As an alternative, I'd suggest pretty much any of the MOUT facilities; there's one at Camp Lejeune that's well-built and even has drainpipes for sub-street-level training, also attachment points on building rooftops for training with in-city assault climbing capabilities.
Failing all of that, though, my vote is for the Alewife red-line stop on the T.
Fort Knox, The White House, The Empire State Building,A costco, And a castle
Fort Knox actually has a pretty hardcore MOUT facility that would be good for Nerfing.