Well, it appears that you know where they are. It is your responsibility to keep below the required altitude. You can say what you want, but it still remains that you are responsible to know.
"Say what you want"?? Did something I said give you the impression that my view of a pilot's responsibility is different from yours? My point isn't that you're free to ignore these airports, it's that it's not a simple matter to find out where the airports near your field are. You can't just get an "aviation map" that shows all the airports near your field. The FAA's web site will list them and give you latitude and longitude, and if you have a decent chart you can plot the locations yourself. Have you ever done this? Very few RC pilots have. Nobody in my club (a group that includes several full-scale pilots) had any idea how many airports we have in the county where most of them have lived for years.