Offline advertising is very tough indeed. The only successful people doing it have very large operating budgets and do CD mailers to targeted lists of gamblers. Results are said to be good but the initial outlay can be a big hurdle for most portal owners.
In the past I advertised on Radio and spent $10k on a test campaign on the Howard Stern show. It was really cool hearing my ads read on the radio, but it did NOT produce any tangible results so I had to drop it.
I briefly toyed with the idea of placing signs on busy intersections. Then I decided the local law enforcement people would probably come after me as they love to legislate morality here in Orlando.
I think from the standpoint of legality and ROI it doesnt make sense to do non-tartgeted or offline advertising in the present business climate.