Exactly how close is the boat ramp flying field?How often do you suspect that you are getting interference?These are the first things that need answered.I cant see anyone risking their own plane knowing they could be interfered with( as the "rogue" guys would be).Is it possible you just crashed your plane?
Now,its been said over and over,but the AMA has no authority here.An AMA card doesnt entitle you to anything.Why should someone that may not be able to afford AMA and club dues not be able to fly?Wait, it doesnt keep them from flying does it?Not saying it doesnt suck,but thats the way it is.If I owned land next to an AMA club field and I want to fly,then guess what,I can.If my aunts uncles cousins second wife has land next to a field and she says I can fly there,then again I can.Doesnt make me an idiot( I saved 58 bucks plus club dues),other than I would be risking my own plane.The boat ramp pilots are breaking no laws,at least not now.The county could pass something that states the need for insurance to fly from public property.Then say they produce a homeowners policy that is basically equal to what you have with the AMA or worse yet,find private land even closer to the club field.It may even be possible for them to form a small non-ama club and force the county to lease them land(Im not clear if the club field is on county land or not) like they have for others.Working with the group that doesnt belong to the club makes the most sense.I highly doubt they would want to lose a plane to interference either.

instead of worrying about what an AMA card will get you in this world,remember the things it will not do for you
1.An AMA card doesnt make you a r/c pilot (my wife has a drivers license,but I still will not ride with her)
2.An AMA card doesnt give you the right to any frequencies(anyone can buy a tx/rx regardless of age,race,religion,or gender)
3.an AMA card doesnt make you smarter than anyone else(read some of the posts on this site)