AM:
Worst:
Las Vegas Strip at night. Daytime brought in all local signals OK. Nighttime is indeed a disaster, though. It is true that you will probably get two stations at best during nighttime hours.
Best:
Outer Banks, NC has excellent AM coverage day and night. WOKV from Jacksonville is a regular 24/7. WCBS is pretty much a regular, too.
FM:
Worst:
The entire Miami/Ft. Lauderdale market is awful for even local broadcasters. Combine dozens of pirates on adjacent frequencies, a crop of legal translators, about 15 class C's on three adjacent towers which absolutely blankets the band between Miami and Ft. Lauderdale. West Palm Beach stations have a tough time making it the 40 miles to Ft. Lauderdale! Only DX I got down there was strong tropo from Ft. Pierce which overran the pirates on 92.7.
Best:
Overall year-round listening goes to most of the Blue Ridge Parkway in VA. You can pick up most of the Richmond signals from 90+ miles away as if they're locals from Lexington to just south of Winchester. NC stations from Raleigh, Greensboro, Fayetteville, and Greenville boom in when there's even a hint of tropo. Mind you, most of the parkway in VA is on the eastern side of the mountains which allows for good views and FM listening.
A "honorable mention" should go to the Atlantic coast between Charleston and Cape Canaveral outside of the big cities. FM DXing is an 8-9 month regular occurence in these parts. It's not uncommon to get FM's from the Carribean during E-skip and long-distance tropo is pretty much a nightly thing from April-October.
Radio-X