Whether the presence of ethanol is required to be posted varies from state to state. Some states require it, some don't. Here in Oregon, it is required, but I have seen pumps without the posting when all they sold had ethanol.
Expect to see more ethanol. Producers have learned that ethanol is a cheaper octane booster than whatever else they used and are using it more and more, even if they are not required to use it. If you don't have ethanol in your gas yet, consider yourself lucky.
When ethanol comes, don't let it sit around--buy only what you need. It absorbs water and is hard on fuel systems not designed for it. It can also separate out and burns differently from pure gas and that can result in problems. Ethanol destroyed my $400 weedeater when we first got it here in Oregon in the early '90's.
Worse yet, the ethanol industry, which is in big time financial problems, has petitioned the government to require 15% ethanol, up from the 10%. Most cars have only been designed for 10% and if it goes thru, you can expect problems, for which the ethanol industry will deny any responsibility.