And, that, specifically: "I think it is illegal to land on a beach in Oregon. I could be wrong but, I don't think so. " is why I suggested to go DIRECTLY to the source of enforcement and the responsible land management agency.
I can tell you from experience, folks, that you will get LOTS of information on this via the internet, and MOST Of it will be flat wrong. But, the good news is that NONE of it means a dang thing

.
I have worked for a land management agency. I've had people lecture me at length, after I contacted them, that it was perfectly legal for them to land their airplane there, cause they were told so by their brother in law--a guy named Bubba. To which I replied, "Gee, my office woulda told you the same dang thing, only it would be official". That kind of response takes the starch right outta a big argument.
The point is this: There are a LOT of different flavors of law enforcement officers out there, county sherrif deputy, highway patrol, city police, various land management agency types, and on and on. In my experience, most county deputies don't know ANYthing about land management rules, but they assume everything is illegal until proven wrong by a court.
SOOOOO, let's assume you talk to the Florida Aeronautics folks. Tell them about a certain beach you'd like to land on. They tell you who the landowner is, which is, say the State. You call whoever there, and ask the question, and they say "go for it".
You are landing on the beach and a county mountie shows up (sorry to pick on the Sherrif's offices here, could be anyone), and starts asking you questions about the legalities of landing there. You give him or her a name and phone number. Conversation over, essentially, cause he'll have dispatch call the number.
That's a whole lot better than landing somewhere based on internet information, and the same thing happens....."Uh, Officer, I read that it was legal on the internet from some guy in Iowa".
If you are really serious about landing on a beach, call the state, and start looking for GOOD information.
MTV