Right,
the ski-lodge is a bit of plot-railroading to pick-up Annabeth, we don't have to stay there, but I figure cars are a mode, the lodges are a location we could easily get to while the stiffs cannot; making it a good rally-point.
Anyways, Rocky-Top Motel and Campground, Highway 24, 2 miles west of Colorado Springs.
-Literally a 1 minute drive to safety. A bit too close to the regional hospital and Santa's Workshop, though.
The resorts are pretty self-sustaining since it's off-grid in a Nat'l park.
Disclaimer: Trying to actually break-into such a resort would likely get the US-Forestry-service, and several private security agencies to bust your ass.
Some of them are built like literal castles, up on steep clifftops even.
Also, it would be fitting to get swarmed in South Park, AKA: Fairplay, Colorado.
-But for te sake of realism, first stop will be just
Rocky Mountain Lodge and cabin. Not quite as upscale (less novelty luxury-'facilities'), but still nice, remote, and well defended (the owners live there, I'm just glad they're super-kind people).
-The street-view is what sold the idea.