Sounds like you have a great outlook on it! If you have not been able to visit many national parks, you are in for a treat. I have had the privledge of visiting a few of the ones in the western US, and am looking forward to doing a LOT of bike touring when I retire (hopefully in about a year). Plan to see a lot more then.

As far as your budget, $1500/mo comes to roughly $50/day! I would think that if you have your gear paid for before you start, that should be plenty for an extended tour.

Depending on when you start, we may be doing the Pacific coast at about the same time. Keep us (the forum) up on your progress, and maybe we'll see each other on the road.