Welcome to the RTA Forum!

We really aren't in a position to give any legal advice, nor should you really be looking to any internet message board to answer questions of what is or is not legal.

Each state has their own laws regarding teen/graduated drivers licenses, and I'm not exactly sure how those are handled across state lines. A general rule of thumb is that what you are allowed to do in your home state you can do elsewhere, but that might not apply in this case. I would strongly suggest that you talk to either your drivers ed instructor or a police officer and perhaps they can give you a better understanding of what you would or would not be allowed to do.

The trip you've laid out could be done, it takes about 1 week to drive coast to coast, so with 2 for each direction you've got some room to work with. Your bigger problems will involve all of the challenges of traveling under age 18. The single biggest one will be lodging, as almost no motels will allow people under 18 to rent a room. Camping would give you some more options, but being in spring, it could still be a pretty cool time of year to camp out every night for a month.

It sounds like you've got a good head on your shoulders and are being thoughtful about what you want to do. Unfortantly, your ages will be a big roadblock and it will be tough to do as big of a trip as you want.