Cape Cod to really far away...
 

Now, you might think I'm crazy, but a friend and myself are leaving on a cross country tour April 1st. (Not a joke)
The plan is to ride from Cape Cod to Atlanta, and then head west to LA from there, and then north to SF. Now, I've only roughly gauged the route using Google Maps for bikes, and have recently purchased a Garmin Edge 800, but rest assured, we'll have regular maps too.
Does anyone have any routes they'd suggest for the Eastern Seaboard? I'm trying to avoid PA due to some unpaid speeding tickets from awhile back...

The only semi-crazy part about your plan is LA to SF. Lots of comments here, on crazyguyonabike.org, and adventurecycling.net regarding the prevailing winds that blow south along the coast and that you are on the inland side of the highway where the views are not as great and the shoulder seems narrower. Also not sure why having unpaid motor vehicle tickets in a state would prevent you from biking through. I've never had a cop stop me on a bike tour.

Have you looked at Adventure Cycling Association's route network? For starters, you could head west and pick up the Atlantic Coast Route south. You would have to modify it a bit since it goes through PA. If you can stand being in the state for about 15 miles, (the route enters PA from NJ at Delaware Water Gap, PA and then crosses back into NJ at Belividere) you could follow the route to Lambertville, NJ and then stay in NJ rather than crossing the river back into PA at New Hope. The D&R canal path, which actually starts around Milford/Frenchtown, NJ (as is part of the AC route) continues southwest from Lambertville, to Trenton, NJ, although portions of it south fo Lambertville may still be closed for reconstruction. To avoid PA completely, you would eventually have to head to Cape May, NJ and take the ferry to Lewes, DE and then figure out how to rejoin the route. I think avoiding PA because of some old speeding tickets is a little silly unless you ride like you drive and might get stopped by a cop.

Second the point about the CA coast. The general consensus is that if you are going to circumnavigate (fully or partially) the country you go counterclockwise.

Stay off Pa expressways and the cops will stay off you. I've been stopped(expressway)a few times but never ID'd. "Sir, you see that exit up there? Take it."

1+ the advice about winds and your route. Either way, you'll encounter days of strong headwinds, especially heading west, but counterclockwise, fewer. I would never consider running the CA coast south to north. Never.

How about Boston airport to Shannon in western Ireland instead?

South to North works there.. Plus the sea will be on the left,
same side of the road as you're on..

When contemplating a long tour, it's wise to do research and ask questions, which I do, much like you're doing. It can make a huge difference in your enjoyment of the trip. As has been cautioned, the prevailing winds blow south (stronger the further south you go). The eastern seaboard is the opposite. Along the south, it's a crap shoot, especially during storm season. Veteran cycle-tourers I've asked say if you're only going one way, go with the prevailing winds, otherwise, go to the farthest point and cycle back....the closer to home, the less likely you'll be inclined to give up, and if you have problems, the cheaper and easier it is to get home.